XWiki Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') Vulnerability (CVE-2023-29202)

Description

XWiki Commons are technical libraries common to several other top level XWiki projects. The RSS macro that is bundled in XWiki included the content of the feed items without any cleaning in the HTML output when the parameter `content` was set to `true`. This allowed arbitrary HTML and in particular also JavaScript injection and thus cross-site scripting (XSS) by specifying an RSS feed with malicious content. With the interaction of a user with programming rights, this could be used to execute arbitrary actions in the wiki, including privilege escalation, remote code execution, information disclosure, modifying or deleting content and sabotaging the wiki. The issue has been patched in XWiki 14.6 RC1, the content of the feed is now properly cleaned before being displayed. As a workaround, if the RSS macro isn't used in the wiki, the macro can be uninstalled by deleting `WEB-INF/lib/xwiki-platform-rendering-macro-rss-XX.jar`, where `XX` is XWiki's version, in the web application's directory.