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GHSA-m3jr-cvhj-f35j
No affected components available
Impact
The "restricted" mode of the HTML cleaner in XWiki, introduced in version 4.2-milestone-1, only escaped <script> and <style>-tags but neither attributes that can be used to inject scripts nor other dangerous HTML tags like <iframe>. As a consequence, any code relying on this "restricted" mode for security is vulnerable to JavaScript injection ("cross-site scripting"/XSS). An example are anonymous comments in XWiki where the HTML macro filters HTML using restricted mode:
{{html}}
<a href='' onclick='alert(1)'>XSS</a>
{{/html}}
When a privileged user with programming rights visits such a comment in XWiki, the malicious JavaScript code is executed in the context of the user session. This allows server-side code execution with programming rights, impacting the confidentiality, integrity and availability of the XWiki instance.
Patches
This problem has been patched in XWiki 14.6 RC1 with the introduction of a filter with allowed HTML elements and attributes that is enabled in restricted mode.
Workarounds
There are no known workarounds apart from upgrading to a version including the fix.
References
- https://github.com/xwiki/xwiki-commons/commit/b11eae9d82cb53f32962056b5faa73f3720c6182 - the patch with the filter
- https://github.com/xwiki/xwiki-commons/commit/4a185e0594d90cd4916d60aa60bb4333dc5623b2 - the patch with the definitions what is allowed
- https://jira.xwiki.org/browse/XWIKI-9118 - the security issue with the HTML macro
- https://jira.xwiki.org/browse/XCOMMONS-1680 - the issue regarding a definition of what is allowed HTML
- https://jira.xwiki.org/browse/XCOMMONS-2426 - the issue regarding the filter that fixes the security issue
For more information
If you have any questions or comments about this advisory:
- Open an issue in Jira XWiki
- Email us at XWiki Security mailing-list
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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