XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. When uploading an attachment with a malicious filename, malicious JavaScript code could be executed. This requires a social engineering attack to get the victim into uploading a file with a malicious name. The malicious code is solely executed during the upload and affects only the user uploading the attachment. While this allows performing actions in the name of that user, it seems unlikely that a user wouldn't notice the malicious filename while uploading the attachment. This has been patched in XWiki 14.10.21, 15.5.5, 15.10.6 and 16.0.0.
https://jira.xwiki.org/browse/XWIKI-21769
https://jira.xwiki.org/browse/XWIKI-19611
https://jira.xwiki.org/browse/XWIKI-19602
https://github.com/xwiki/xwiki-platform/security/advisories/GHSA-wf3x-jccf-5g5g
https://github.com/xwiki/xwiki-platform/commit/9df46f8e5313af46f93bccd1ebc682e28126573f
https://github.com/xwiki/xwiki-platform/commit/910a5018a50039e8b24556573dfe342f143ef949
https://github.com/xwiki/xwiki-platform/commit/8b8a2d80529b9a9c038014c1eb6c2adc08069dfd
https://github.com/xwiki/xwiki-platform/commit/6cdd69d31d6bf3caa7f40ec55eb317e4e528ad28