Discourse is an open source discussion platform. Version before 3.6.2 and 3.6.0.beta2, default Cache-Control response header with value no-store, no-cache was missing from error responses. This may caused unintended caching of those responses by proxies potentially leading to cache poisoning attacks. This vulnerability is fixed in 3.6.2 and 3.6.0.beta2.
https://github.com/discourse/discourse/security/advisories/GHSA-jp9x-wwv6-cv3j
https://github.com/discourse/discourse/commit/fd567af7bf5a15c70772021acbdf5d38487a31bc
https://github.com/discourse/discourse/commit/3ea1b663c82c067e5ca778db846bad1e082ba6cd