CVE-2025-49581: XWiki allows remote code execution through default value of wiki macro wiki-type parameters

Any user with edit right on a page (could be the user’s profile) can execute code (Groovy, Python, Velocity) with programming right by defining a wiki macro. This allows full access to the whole XWiki installation and thus impacts its confidentiality, integrity and availability. The main problem is that if a wiki macro parameter allows wiki syntax, its default value is executed with the rights of the author of the document where it is used. This can be exploited by overriding a macro like the children macro that is used in a page that has programming right like the page XWiki.ChildrenMacro and thus allows arbitrary script macros. The full reproduction steps can be found in the original issue.