Users are able to forge an URL with a payload allowing to inject Javascript in the page (XSS).
For instance, the following URL execute an alter on the browser: <xwiki-host>/xwiki/bin/view/Main/?viewer=share&send=1&target=&target=%3Cimg+src+onerror%3Dalert%28document.domain%29%3E+%3Cimg+src+onerror%3Dalert%28document.domain%29%3E+%3Crenniepak%40intigriti.me%3E&includeDocument=inline&message=I+wanted+to+share+this+page+with+you., where <xwiki-host> is the URL of your XWiki installation.
See https://jira.xwiki.org/browse/XWIKI-20370 for me details.
The vulnerability has been patched in XWiki 15.0-rc-1, 14.10.4, and 14.4.8.
The fix is only impacting Velocity templates and page contents, so applying this patch is enough to fix the issue.
https://jira.xwiki.org/browse/XWIKI-20370
If you have any questions or comments about this advisory:
This vulnerability has been reported on Intigriti by René de Sain @renniepak.
{
    "github_reviewed_at": "2023-06-20T16:48:36Z",
    "severity": "HIGH",
    "github_reviewed": true,
    "cwe_ids": [
        "CWE-79"
    ],
    "nvd_published_at": "2023-06-23T19:15:09Z"
}