GHSA-663w-2xp3-5739

### Impact
The cleaning of attributes during XHTML rendering, introduced in version 14.6-rc-1, allowed the injection of arbitrary HTML code and thus cross-site scripting via invalid attribute names. 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||/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.

While this attribute was correctly recognized as not allowed, the attribute was still printed with a prefix `data-xwiki-translated-attribute-` without further cleaning or validation.

Note that while versions below 14.6 are not vulnerable to this particular vulnerability, they are still vulnerable to XSS through attributes in XWiki syntax, see [the corresponding advisory](https://github.com/xwiki/xwiki-rendering/security/advisories/GHSA-6gf5-c898-7rxp).

### Patches
This problem has been patched in XWiki 14.10.4 and 15.0 RC1 by removing characters not allowed in data attributes and then validating the cleaned attribute again.

### Workarounds
There are no known workarounds apart from upgrading to a version including the fix.

### References
* https://jira.xwiki.org/browse/XRENDERING-697
* https://github.com/xwiki/xwiki-rendering/commit/f4d5acac451dccaf276e69f0b49b72221eef5d2f

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [Jira XWiki](https://jira.xwiki.org/)
* Email us at [XWiki Security mailing-list](mailto:[email protected])