XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. When an admin disables a user account, the users profile is executed with the admins rights. This allows a user to place malicious code in the user profile before getting an admin to disable the user account. To reproduce, as a user without script nor programming rights, edit the about section of your user profile and add {{groovy}}services.logging.getLogger(attacker).error(Hello from Groovy!){{/groovy}}
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As an admin, go to the user profile and click the Disable this account button. Then, reload the page. If the logs show attacker - Hello from Groovy!
then the instance is vulnerable. This has been patched in XWiki 14.10.21, 15.5.5, 15.10.6 and 16.0.0. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Were not aware of any workaround except upgrading.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
When a product allows a user’s input to contain code syntax, it might be possible for an attacker to craft the code in such a way that it will alter the intended control flow of the product. Such an alteration could lead to arbitrary code execution. Injection problems encompass a wide variety of issues – all mitigated in very different ways. For this reason, the most effective way to discuss these weaknesses is to note the distinct features which classify them as injection weaknesses. The most important issue to note is that all injection problems share one thing in common – i.e., they allow for the injection of control plane data into the user-controlled data plane. This means that the execution of the process may be altered by sending code in through legitimate data channels, using no other mechanism. While buffer overflows, and many other flaws, involve the use of some further issue to gain execution, injection problems need only for the data to be parsed. The most classic instantiations of this category of weakness are SQL injection and format string vulnerabilities.