GHSA-6xxr-648m-gch6

### Impact

The REST API allows executing all actions via POST requests and accepts `text/plain`, `multipart/form-data` or `application/www-form-urlencoded` as content types which can be sent via regular HTML forms, thus allowing cross-site request forgery. With the interaction of a user with programming rights, this allows remote code execution through script macros and thus impacts the integrity, availability and confidentiality of the whole XWiki installation.

For regular cookie-based authentication, the vulnerability is mitigated by SameSite cookie restrictions but as of March 2023, these are not enabled by default in Firefox and Safari.

### Patches
The vulnerability has been patched in XWiki 14.10.8 and 15.2 by requiring a CSRF token header for certain request types that are susceptible to CSRF attacks.

### Workarounds

It is possible to check for the `Origin` header in a reverse proxy to protect the REST endpoint from CSRF attacks, see [the Jira issue](https://jira.xwiki.org/browse/XWIKI-20135) for an example configuration.

### References

* https://jira.xwiki.org/browse/XWIKI-20135
* https://github.com/xwiki/xwiki-platform/commit/4c175405faa0e62437df397811c7526dfc0fbae7