Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, regular users could route direct S3 multipart uploads through ExternalUploadManager into the admin backup store. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.
https://github.com/discourse/discourse/security/advisories/GHSA-3mvf-q9rg-w6m7
https://github.com/discourse/discourse/releases/tag/v2026.6.0
https://github.com/discourse/discourse/releases/tag/v2026.5.1
https://github.com/discourse/discourse/releases/tag/v2026.4.2
https://github.com/discourse/discourse/releases/tag/v2026.1.5
https://github.com/discourse/discourse/commit/abaa664c5df84026efb2ca264ba0f5586c3f2b01
https://github.com/discourse/discourse/commit/a53df26dcf7e50ce2b20bfd5454a0c9d44b8fc7d
https://github.com/discourse/discourse/commit/7ddde266617b452152c1bf5f903f6c07be38fc40
https://github.com/discourse/discourse/commit/1f1ded8dd361d81786bff17b35e1138d6ee299c0