XWiki Rendering is vulnerable to RCE attacks when processing nested macros

XWiki Rendering is a generic rendering system that converts textual input in a given syntax (wiki syntax, HTML, etc) into another syntax (XHTML, etc). Starting in version 4.2-milestone-1 and prior to versions 13.10.11, 14.4.7, and 14.10, the default macro content parser doesn't preserve the restricted attribute of the transformation context when executing nested macros. This allows executing macros that are normally forbidden in restricted mode, in particular script macros. The cache and chart macros that are bundled in XWiki use the vulnerable feature. This has been patched in XWiki 13.10.11, 14.4.7 and 14.10. To avoid the exploitation of this bug, comments can be disabled for untrusted users until an upgrade to a patched version has been performed. Note that users with edit rights will still be able to add comments via the object editor even if comments have been disabled.