Applying a patch manually
Download the 2113patch.zip file attached to this message. It will contain the following file:
- src/XF/BbCode/Renderer/EditorHtml.php
Extract the zip file to your computer and upload the contents to the root of your XenForo installation. This should overwrite the files on your server with the new version.
Note: If you decide to patch the files instead of doing a full upgrade, your "File health check" will report this file as having "Unexpected contents". Because these files no longer contain the same contents your version of XF was shipped with, this is expected and can be safely ignored.