Should messages in WP_Error already be html escaped?












2















This isn't about what html escaping is or how it's done, but if there's an established best practice about when to do it.



I have some utility code in my plugin that may generate a WP_Error based on user input, and other display code that shows that WP_Error. Of course that user input needs to be html escaped when displaying, but I'm not sure when would be the best time to do it.



I have a choice about whether to:




  • Escape the message as I'm constructing the WP_Error, and the display code shows it as-is.


  • Don't worry about escaping when constructing the WP_Error, and in the display code fully escape all the WP_Error messages.



Either would work, but if my plugin ends up interacting with other plugins and possibly displaying their WP_Error or vice-versa, I'd like to match whatever precedent exists in the Wordpress world.



I had hoped the documentation would address this, but I didn't see anything on https://codex.wordpress.org/Class_Reference/WP_Error










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    2















    This isn't about what html escaping is or how it's done, but if there's an established best practice about when to do it.



    I have some utility code in my plugin that may generate a WP_Error based on user input, and other display code that shows that WP_Error. Of course that user input needs to be html escaped when displaying, but I'm not sure when would be the best time to do it.



    I have a choice about whether to:




    • Escape the message as I'm constructing the WP_Error, and the display code shows it as-is.


    • Don't worry about escaping when constructing the WP_Error, and in the display code fully escape all the WP_Error messages.



    Either would work, but if my plugin ends up interacting with other plugins and possibly displaying their WP_Error or vice-versa, I'd like to match whatever precedent exists in the Wordpress world.



    I had hoped the documentation would address this, but I didn't see anything on https://codex.wordpress.org/Class_Reference/WP_Error










    share|improve this question









    New contributor




    Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.























      2












      2








      2








      This isn't about what html escaping is or how it's done, but if there's an established best practice about when to do it.



      I have some utility code in my plugin that may generate a WP_Error based on user input, and other display code that shows that WP_Error. Of course that user input needs to be html escaped when displaying, but I'm not sure when would be the best time to do it.



      I have a choice about whether to:




      • Escape the message as I'm constructing the WP_Error, and the display code shows it as-is.


      • Don't worry about escaping when constructing the WP_Error, and in the display code fully escape all the WP_Error messages.



      Either would work, but if my plugin ends up interacting with other plugins and possibly displaying their WP_Error or vice-versa, I'd like to match whatever precedent exists in the Wordpress world.



      I had hoped the documentation would address this, but I didn't see anything on https://codex.wordpress.org/Class_Reference/WP_Error










      share|improve this question









      New contributor




      Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.












      This isn't about what html escaping is or how it's done, but if there's an established best practice about when to do it.



      I have some utility code in my plugin that may generate a WP_Error based on user input, and other display code that shows that WP_Error. Of course that user input needs to be html escaped when displaying, but I'm not sure when would be the best time to do it.



      I have a choice about whether to:




      • Escape the message as I'm constructing the WP_Error, and the display code shows it as-is.


      • Don't worry about escaping when constructing the WP_Error, and in the display code fully escape all the WP_Error messages.



      Either would work, but if my plugin ends up interacting with other plugins and possibly displaying their WP_Error or vice-versa, I'd like to match whatever precedent exists in the Wordpress world.



      I had hoped the documentation would address this, but I didn't see anything on https://codex.wordpress.org/Class_Reference/WP_Error







      plugins errors escaping






      share|improve this question









      New contributor




      Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question









      New contributor




      Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this question




      share|improve this question








      edited 10 hours ago







      Jason Viers













      New contributor




      Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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      asked 10 hours ago









      Jason ViersJason Viers

      1134




      1134




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      New contributor





      Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      Jason Viers is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






















          3 Answers
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          No, escaping should happen at the moment of output ( late escaping ) so that we know that it only occurs once. Double escaping can allow specially crafted output to break out.



          Since WP_Error does not output, and is not responsible for outputting, it should not perform any escaping internally, nor should its inputs be escaped. Validated/sanitised perhaps, but not escaped.



          If we did escape on input, we would either have to double escape, or trust all WP_Error objects, which is a non-starter.



          So instead, the code that recieves and outputs the WP_Error object is where the escaping should be, that way we escape on output safe in the knowledge that no early escaping has occurred, no double escaping happens, wether it's been escaped is not a problem we have to deal with, and the responsibility for escaping is clear and straight forward






          share|improve this answer
























          • "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

            – Jason Viers
            1 hour ago





















          1














          It's a very good question.



          WP_Error class doesn't do anything with messages you set. So what you set is what you get ;)



          On the other hand, the error messages can contain HTML, so you can't escape all of them, when printing errors. For example here you get a message from wp-login.php file:



          $errors->add('empty_username', __('<strong>ERROR</strong>: Enter a username or email address.'));


          And to make things even harder - as you can see - it's passed through __() function, so after translation the message may contain even more HTML tags.



          All of that means that you should take care of escaping data that may be harmful and remember that errors can contain HTML tags when printing them.






          share|improve this answer
























          • This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

            – Jason Viers
            1 hour ago



















          0














          Personally, I'd keep the error messages basically plain text and static (don't include the user's input) - from what I've seen, most plugins take this mindset of error messages being short text-only notes of what has gone wrong. This allows you to use messages like "Password is too short" vs "'MyPass' is to short of a password".



          If you need some HTML in the error message itself, I'd escape it on the way in.



          $error = new WP_Error();

          $message = "The correct tag is <strong></strong>";
          $html_ok_message = htmlspecialchars($message);

          $error->add($code, $html_ok_message, $data);


          You could escape them on the way out if you know all the possible errors encountered have no HTML that needs to be displayed. If you escape them all always when outputting, you'll likely end up with things like &lt;strong;Error&gt; Something went wrong in XY_Other_plugin .






          share|improve this answer























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            3 Answers
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            active

            oldest

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            3 Answers
            3






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

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            3














            No, escaping should happen at the moment of output ( late escaping ) so that we know that it only occurs once. Double escaping can allow specially crafted output to break out.



            Since WP_Error does not output, and is not responsible for outputting, it should not perform any escaping internally, nor should its inputs be escaped. Validated/sanitised perhaps, but not escaped.



            If we did escape on input, we would either have to double escape, or trust all WP_Error objects, which is a non-starter.



            So instead, the code that recieves and outputs the WP_Error object is where the escaping should be, that way we escape on output safe in the knowledge that no early escaping has occurred, no double escaping happens, wether it's been escaped is not a problem we have to deal with, and the responsibility for escaping is clear and straight forward






            share|improve this answer
























            • "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

              – Jason Viers
              1 hour ago


















            3














            No, escaping should happen at the moment of output ( late escaping ) so that we know that it only occurs once. Double escaping can allow specially crafted output to break out.



            Since WP_Error does not output, and is not responsible for outputting, it should not perform any escaping internally, nor should its inputs be escaped. Validated/sanitised perhaps, but not escaped.



            If we did escape on input, we would either have to double escape, or trust all WP_Error objects, which is a non-starter.



            So instead, the code that recieves and outputs the WP_Error object is where the escaping should be, that way we escape on output safe in the knowledge that no early escaping has occurred, no double escaping happens, wether it's been escaped is not a problem we have to deal with, and the responsibility for escaping is clear and straight forward






            share|improve this answer
























            • "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

              – Jason Viers
              1 hour ago
















            3












            3








            3







            No, escaping should happen at the moment of output ( late escaping ) so that we know that it only occurs once. Double escaping can allow specially crafted output to break out.



            Since WP_Error does not output, and is not responsible for outputting, it should not perform any escaping internally, nor should its inputs be escaped. Validated/sanitised perhaps, but not escaped.



            If we did escape on input, we would either have to double escape, or trust all WP_Error objects, which is a non-starter.



            So instead, the code that recieves and outputs the WP_Error object is where the escaping should be, that way we escape on output safe in the knowledge that no early escaping has occurred, no double escaping happens, wether it's been escaped is not a problem we have to deal with, and the responsibility for escaping is clear and straight forward






            share|improve this answer













            No, escaping should happen at the moment of output ( late escaping ) so that we know that it only occurs once. Double escaping can allow specially crafted output to break out.



            Since WP_Error does not output, and is not responsible for outputting, it should not perform any escaping internally, nor should its inputs be escaped. Validated/sanitised perhaps, but not escaped.



            If we did escape on input, we would either have to double escape, or trust all WP_Error objects, which is a non-starter.



            So instead, the code that recieves and outputs the WP_Error object is where the escaping should be, that way we escape on output safe in the knowledge that no early escaping has occurred, no double escaping happens, wether it's been escaped is not a problem we have to deal with, and the responsibility for escaping is clear and straight forward







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered 6 hours ago









            Tom J NowellTom J Nowell

            32.1k44796




            32.1k44796













            • "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

              – Jason Viers
              1 hour ago





















            • "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

              – Jason Viers
              1 hour ago



















            "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

            – Jason Viers
            1 hour ago







            "or trust all WP_Error objects, which is a non-starter" This essentially answers my question. Definitely sounds like WP_Error cannot be assumed to contain html escaped content, therefore WP_Errors MUST be escaped when displayed.

            – Jason Viers
            1 hour ago















            1














            It's a very good question.



            WP_Error class doesn't do anything with messages you set. So what you set is what you get ;)



            On the other hand, the error messages can contain HTML, so you can't escape all of them, when printing errors. For example here you get a message from wp-login.php file:



            $errors->add('empty_username', __('<strong>ERROR</strong>: Enter a username or email address.'));


            And to make things even harder - as you can see - it's passed through __() function, so after translation the message may contain even more HTML tags.



            All of that means that you should take care of escaping data that may be harmful and remember that errors can contain HTML tags when printing them.






            share|improve this answer
























            • This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

              – Jason Viers
              1 hour ago
















            1














            It's a very good question.



            WP_Error class doesn't do anything with messages you set. So what you set is what you get ;)



            On the other hand, the error messages can contain HTML, so you can't escape all of them, when printing errors. For example here you get a message from wp-login.php file:



            $errors->add('empty_username', __('<strong>ERROR</strong>: Enter a username or email address.'));


            And to make things even harder - as you can see - it's passed through __() function, so after translation the message may contain even more HTML tags.



            All of that means that you should take care of escaping data that may be harmful and remember that errors can contain HTML tags when printing them.






            share|improve this answer
























            • This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

              – Jason Viers
              1 hour ago














            1












            1








            1







            It's a very good question.



            WP_Error class doesn't do anything with messages you set. So what you set is what you get ;)



            On the other hand, the error messages can contain HTML, so you can't escape all of them, when printing errors. For example here you get a message from wp-login.php file:



            $errors->add('empty_username', __('<strong>ERROR</strong>: Enter a username or email address.'));


            And to make things even harder - as you can see - it's passed through __() function, so after translation the message may contain even more HTML tags.



            All of that means that you should take care of escaping data that may be harmful and remember that errors can contain HTML tags when printing them.






            share|improve this answer













            It's a very good question.



            WP_Error class doesn't do anything with messages you set. So what you set is what you get ;)



            On the other hand, the error messages can contain HTML, so you can't escape all of them, when printing errors. For example here you get a message from wp-login.php file:



            $errors->add('empty_username', __('<strong>ERROR</strong>: Enter a username or email address.'));


            And to make things even harder - as you can see - it's passed through __() function, so after translation the message may contain even more HTML tags.



            All of that means that you should take care of escaping data that may be harmful and remember that errors can contain HTML tags when printing them.







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered 8 hours ago









            Krzysiek DróżdżKrzysiek Dróżdż

            14.4k52742




            14.4k52742













            • This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

              – Jason Viers
              1 hour ago



















            • This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

              – Jason Viers
              1 hour ago

















            This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

            – Jason Viers
            1 hour ago





            This was the difficulty I was imagining - if my display code somehow ended up getting a hold of the WP_Error with that add()-ed message, it will display literal <strong> tags to the user. But it sounds like it's unsafe to assume that tags in WP_Error are "intentional from devs and safe", so it'll have to be escaped on display.

            – Jason Viers
            1 hour ago











            0














            Personally, I'd keep the error messages basically plain text and static (don't include the user's input) - from what I've seen, most plugins take this mindset of error messages being short text-only notes of what has gone wrong. This allows you to use messages like "Password is too short" vs "'MyPass' is to short of a password".



            If you need some HTML in the error message itself, I'd escape it on the way in.



            $error = new WP_Error();

            $message = "The correct tag is <strong></strong>";
            $html_ok_message = htmlspecialchars($message);

            $error->add($code, $html_ok_message, $data);


            You could escape them on the way out if you know all the possible errors encountered have no HTML that needs to be displayed. If you escape them all always when outputting, you'll likely end up with things like &lt;strong;Error&gt; Something went wrong in XY_Other_plugin .






            share|improve this answer




























              0














              Personally, I'd keep the error messages basically plain text and static (don't include the user's input) - from what I've seen, most plugins take this mindset of error messages being short text-only notes of what has gone wrong. This allows you to use messages like "Password is too short" vs "'MyPass' is to short of a password".



              If you need some HTML in the error message itself, I'd escape it on the way in.



              $error = new WP_Error();

              $message = "The correct tag is <strong></strong>";
              $html_ok_message = htmlspecialchars($message);

              $error->add($code, $html_ok_message, $data);


              You could escape them on the way out if you know all the possible errors encountered have no HTML that needs to be displayed. If you escape them all always when outputting, you'll likely end up with things like &lt;strong;Error&gt; Something went wrong in XY_Other_plugin .






              share|improve this answer


























                0












                0








                0







                Personally, I'd keep the error messages basically plain text and static (don't include the user's input) - from what I've seen, most plugins take this mindset of error messages being short text-only notes of what has gone wrong. This allows you to use messages like "Password is too short" vs "'MyPass' is to short of a password".



                If you need some HTML in the error message itself, I'd escape it on the way in.



                $error = new WP_Error();

                $message = "The correct tag is <strong></strong>";
                $html_ok_message = htmlspecialchars($message);

                $error->add($code, $html_ok_message, $data);


                You could escape them on the way out if you know all the possible errors encountered have no HTML that needs to be displayed. If you escape them all always when outputting, you'll likely end up with things like &lt;strong;Error&gt; Something went wrong in XY_Other_plugin .






                share|improve this answer













                Personally, I'd keep the error messages basically plain text and static (don't include the user's input) - from what I've seen, most plugins take this mindset of error messages being short text-only notes of what has gone wrong. This allows you to use messages like "Password is too short" vs "'MyPass' is to short of a password".



                If you need some HTML in the error message itself, I'd escape it on the way in.



                $error = new WP_Error();

                $message = "The correct tag is <strong></strong>";
                $html_ok_message = htmlspecialchars($message);

                $error->add($code, $html_ok_message, $data);


                You could escape them on the way out if you know all the possible errors encountered have no HTML that needs to be displayed. If you escape them all always when outputting, you'll likely end up with things like &lt;strong;Error&gt; Something went wrong in XY_Other_plugin .







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 8 hours ago









                DACrosbyDACrosby

                29817




                29817






















                    Jason Viers is a new contributor. Be nice, and check out our Code of Conduct.










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