Unread bookmark reminder notifications that the user cannot access can be seen

Vulnerability Description

Discourse is an open source platform for community discussion. Prior to version 3.1.3 of the `stable` branch and version 3.2.0.beta3 of the `beta` and `tests-passed` branches, there is an edge case where a bookmark reminder is sent and an unread notification is generated, but the underlying bookmarkable (e.g. post, topic, chat message) security has changed, making it so the user can no longer access the underlying resource. As of version 3.1.3 of the `stable` branch and version 3.2.0.beta3 of the `beta` and `tests-passed` branches, bookmark reminders are now no longer sent if the user does not have access to the underlying bookmarkable, and also the unread bookmark notifications are always filtered by access. There are no known workarounds.

References

• https://github.com/discourse/discourse/security/advisories/GHSA-v9r6-92wp-f6cf
• https://github.com/discourse/discourse/commit/2c45b949ea0e9d6fa8e5af2dd07f6521ede08bf1
• https://github.com/discourse/discourse/commit/3c5fb871c0f54af47679ae71ad449666b01d8216