Reflected XSS in Gotify's /docs via import of outdated Swagger UI

Impact

Gotify exposes an outdated instance of the Swagger UI API documentation frontend at /docs which is susceptible to reflected XSS attacks when loading external Swagger config files.

Specifically, the DOMPurify version included with this version of Swagger UI is vulnerable to a rendering XSS incorporating the mutation payload detailed in CVE-2020-26870 which was patched in 2021. This is further tracked in the GitHub Advisory Database as GHSA-QRMM-W75W-3WPX.

An attacker can execute arbitrary JavaScript and potentially take over the account of the user that clicked the link. Keep in mind, the Gotify UI won't natively expose such a malicious link, so an attacker has to get the user to open the malicious link in a context outside of Gotify.

Patches

The vulnerability has been fixed in version 2.2.3.

References

https://github.com/gotify/server/pull/541