Headline
CVE-2023-31126: HTML element sanitizer accepts invalid data attributes, allowing XSS
org.xwiki.commons:xwiki-commons-xml is an XML library used by the open-source wiki platform XWiki. The HTML sanitizer, introduced in version 14.6-rc-1, allows the injection of arbitrary HTML code and thus cross-site scripting via invalid data attributes. This vulnerability does not affect restricted cleaning in HTMLCleaner as there attributes are cleaned and thus characters like / and > are removed in all attribute names. This problem has been patched in XWiki 14.10.4 and 15.0 RC1 by making sure that data attributes only contain allowed characters. There are no known workarounds apart from upgrading to a version including the fix.
Steps to Reproduce:
Add the attribute data-x/onmouseover="alert(‘XSS1’)" to any element like a link: [[Link1>>https://XWiki.example.com||data-x/onmouseover="alert(‘XSS1’)"]].
Expected Result:
The attribute is rejected by the sanitizer and no alert is displayed when moving the mouse over the link.
Actual Result:
The attribute is accepted by the sanitizer and an alert is displayed when moving the mouse over the link.
Note that restricted cleaning in the HTMLCleaner is not affected by this vulnerability as HTMLCleaner properly parses data-x/onmouseover as two different attributes, or in other words, this cannot be exploited through the HTML macro.
Related news
### Impact The HTML sanitizer, introduced in version 14.6-rc-1, allowed the injection of arbitrary HTML code and thus cross-site scripting via invalid data attributes. This can be exploited, e.g., via the link syntax in any content that supports XWiki syntax like comments in XWiki: ``` [[Link1>>https://XWiki.example.com||data-x/onmouseover="alert('XSS1')"]]. ``` When a user moves the mouse over this link, the malicious JavaScript code is executed in the context of the user session. When this user is a privileged user who has programming rights, this allows server-side code execution with programming rights, impacting the confidentiality, integrity and availability of the XWiki instance. Note that this vulnerability does not affect restricted cleaning in HTMLCleaner as there attributes are cleaned and thus characters like `/` and `>` are removed in all attribute names. ### Patches This problem has been patched in XWiki 14.10.4 and 15.0 RC1 by making sure that data attributes only c...