XWiki Commons are technical libraries common to several other top level XWiki projects. There was no check in the author of a JavaScript xobject or StyleSheet xobject added in a XWiki document, so until now it was possible for a user having only Edit Right to create such object and to craft a script allowing to perform some operations when executing by a user with appropriate rights. This has been patched in XWiki 14.9-rc-1 by only executing the script if the author of it has Script rights.
XWiki Commons are technical libraries common to several other top level XWiki projects. 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). 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. 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. There are no known workarounds apart from upgrading to a version including the fix.
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.
XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. It's possible to make the farm unusable by adding an object to a page with a huge number (e.g. 67108863). Most of the time this will fill the memory allocated to XWiki and make it unusable every time this document is manipulated. This issue has been patched in XWiki 14.0-rc-1.