CVE-2023-29528

### Impact The "restricted" mode of the HTML cleaner in XWiki, introduced in version 4.2-milestone-1 and massively improved in version 14.6-rc-1, allowed the injection of arbitrary HTML code and thus cross-site scripting via invalid HTML comments. 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 {{html}} <!--> <Details Open OnToggle=confirm("XSS")> {{/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. Note that while all versions since 4.2-milestone-1 should be vulnerable, only starting with version 14.6-rc-1 the HTML comment is necessary for the attack to succeed due to [another vulnerability](https://github.com/xwiki/xwiki-commons/security/advisories/GHSA-m3jr-cvhj-f35j) that has been patched in version 14.6-rc-1. ### Patches This problem has been patched in XWiki 14.10, HTML comments are now removed in restricted mode and a check has been introduced that ensures that comments don't start with `>`. ### Workarounds There are no known workarounds apart from upgrading to a version including the fix. ### References * https://jira.xwiki.org/browse/XCOMMONS-2568 * https://jira.xwiki.org/browse/XWIKI-20348 * https://github.com/xwiki/xwiki-commons/commit/8ff1a9d7e5d7b45b690134a537d53dc05cae04ab ### 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:security@xwiki.org) ### Attribution This vulnerability was reported on Intigriti by [ynoof](https://twitter.com/ynoofAssiri) @Ynoof5.