Impact When the realtime editor is installed in XWiki, it allows arbitrary remote code execution with the interaction of an admin user with programming right. More precisely, by getting an admin user to either visit a crafted URL or to view an image with this URL that could be in a comment, the attacker can get the admin to execute arbitrary XWiki syntax including scripting macros with Groovy or Python code. This compromises the confidentiality, integrity and availability of the whole XWiki installation.

To reproduce on an XWiki installation, as an admin, click on <xwiki-host>/xwiki/bin/get/RTFrontend/ConvertHTML?wiki=xwiki&space=Main&page=WebHome&text=%7B%7Bvelocity%7D%7D%24logtool.error%28%22Hello%20from%20Velocity%20%21%22%29%7B%7B%2Fvelocity%7D%7D. If the error "Hello from Velocity!" gets logged then the installation is vulnerable.

Patches This vulnerability has been patched in XWiki 14.10.19, 15.5.4 and 15.9.

Workarounds Update RTFrontend.ConvertHTML following this patch. This will, however, break some synchronization processes in the realtime editor, so upgrading should be the preferred way on installations where this editor is used.

References https://jira.xwiki.org/browse/XWIKI-21424 https://github.com/xwiki/xwiki-platform/commit/4896712ee6483da623f131be2e618f1f2b79cb8d

Impact

NOTE: The Realtime WYSIWYG Editor extension was experimental, and thus not recommended, in the versions affected by this vulnerability. It has become enabled by default, and thus recommended, starting with XWiki 16.9.0.

A user with only edit right can join a realtime editing session where others, that where already there or that may join later, have script or programming access rights. This user can then insert script rendering macros that are executed for those users in the realtime session that have script or programming rights. The inserted scripts can be used to gain more access rights.

Here's an example that works with XWiki 15.10.9+ and 16.2.0+:

the attacker starts editing a wiki page in realtime (for which they have edit right) another user, with script or programming access right joins the editing session (e.g. by clicking on a link / URL provided by the attacker) the attacker inserts a script rendering macro, say {{velocity}}I can run scripts{{/velocity}}, in the edited content, using the WYSIWYG editor UI the edited content is reloaded for both the attacker and the other user, in order to render the inserted macro the attacker gets a rendering error message the other user sees "I can run scripts"

The attacker can obviously use more advanced scripts to gain access rights.

Before XWiki 15.10.9 and 16.2.0 the edited content was not re-rendered for all the users in the editing sesesion, but only for the user that inserted the macro. This means that in order to reproduce the problem the other user had to insert or update a macro or save and view the content.

Patches

This vulnerability has been patched in XWiki 15.10.12, 16.4.1 and 16.6.0-rc-1.

Workarounds

To avoid this vulnerability you can:

either disable the realtime WYSIWYG editing by disabling the xwiki-realtime CKEditor plugin from the WYSIWYG editor administration section or uninstall the Realtime WYSIWYG Editor extension (org.xwiki.platform:xwiki-platform-realtime-wysiwyg-ui)

References

https://jira.xwiki.org/browse/XWIKI-21949

For more information

If you have any questions or comments about this advisory:

Open an issue in Jira XWiki.org Email us at Security Mailing List

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. A guest user without the right to view pages of the wiki can still list documents by rendering some velocity documents. The problem has been patched in XWiki versions 12.10.11, 13.4.4, and 13.9-rc-1. There is no known workaround for this problem.

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. A guest user without the right to view pages of the wiki can still list documents related to users of the wiki. The problem has been patched in XWiki versions 12.10.11, 13.4.4, and 13.9-rc-1. There is no known workaround for this problem.

XWiki Commons are technical libraries common to several other top level XWiki projects. It's possible to list some users who are normally not viewable from subwiki by requesting users on a subwiki which allows only global users with uorgsuggest.vm. This issue only concerns hidden users from main wiki. Note that the disclosed information are the username and the first and last name of users, no other information is leaked. The problem has been patched on XWiki 13.10.8, 14.4.3 and 14.7RC1.