Gitea substitutes a URL derived from the markup Context field into external renderer command templates without escaping the reference path before shell-style argument splitting. A crafted Context can inject additional renderer arguments, including options that load executable filter files. On deployments using a susceptible external renderer such as pandoc, a user who can place a filter file at an accessible path can cause it to execute as the Gitea service account; the public repository markup endpoint itself can be reachable without authentication.
https://github.com/go-gitea/gitea/security/advisories/GHSA-579w-82gf-89m2
https://github.com/go-gitea/gitea/releases/tag/v1.27.2
https://github.com/go-gitea/gitea/pull/38898
https://github.com/go-gitea/gitea/pull/38885