Adding attachments to a release checked the repository and release of an attachment but not whether it was already linked to an issue or comment. A user with write access to the releases of a repository, who knew the UUID of an attachment in that repository, could link it to a release. This exposed the file name, size and download count of the attachment through the release and allowed the user to rename or delete it.
https://github.com/go-gitea/gitea/security/advisories/GHSA-cwq7-782w-pxcc
https://github.com/go-gitea/gitea/releases/tag/v28.2.0
https://github.com/go-gitea/gitea/pull/39847
https://github.com/go-gitea/gitea/pull/39839