XWiki Platform is a generic wiki platform. Starting in version 3.3-milestone-1 and prior to versions 15.10.9 and 16.3.0, on instances where Extension Repository Application is installed, any user can execute any code requiring programming rights on the server. This vulnerability has been fixed in XWiki 15.10.9 and 16.3.0. Since Extension Repository Application is not mandatory, it can be safely disabled on instances that do not use it as a workaround. It is also possible to manually apply the patches from commit 8659f17d500522bf33595e402391592a35a162e8 to the page ExtensionCode.ExtensionSheet and to the page ExtensionCode.ExtensionAuthorsDisplayer.
Weakness
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before inserting the input into an executable resource, such as a library, configuration file, or template.
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
References