Discourse is an open-source discussion platform. In version 2.8.13 and prior on the `stable` branch and version 2.9.0.beta14 and prior on the `beta` and `tests-passed` branches, any authenticated user can create an unlisted topic. These topics, which are not readily available to other users, can take up unnecessary site resources. A patch for this issue is available in the `main` branch of Discourse. There are no known workarounds available.

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, some theme components allow users to add svgs with unlimited `height` attributes, and this can affect the availability of subsequent replies in a topic. Most Discourse instances are unaffected, only instances with the svgbob or the mermaid theme component are within scope. The issue is patched in version 3.1.3 of the `stable` branch and version 3.2.0.beta3 of the `beta` and `tests-passed` branches. As a workaround, disable or remove the relevant theme components.

Discourse is an open-source discussion platform. Prior to version 2.9.0.beta13, users can post chat messages of an unlimited length, which can cause a denial of service for other users when posting huge amounts of text. Users should upgrade to version 2.9.0.beta13, where a limit has been introduced. No known workarounds are available.

A denial-of-service vulnerability in Mattermost allows an authenticated user to crash the server via multiple large autoresponder messages.

A denial-of-service vulnerability in the Mattermost Playbooks plugin allows an authenticated user to crash the server via multiple large requests to one of the Playbooks API endpoints.

Discourse is an open source discussion platform. In versions prior to 2.8.9 on the `stable` branch and prior to 2.9.0.beta10 on the `beta` and `tests-passed` branches, a malicious actor can add large payloads of text into the Location and Website fields of a user profile, which causes issues for other users when loading that profile. A fix to limit the length of user input for these fields is included in version 2.8.9 on the `stable` branch and version 2.9.0.beta10 on the `beta` and `tests-passed` branches. There are no known workarounds.

The Sieve engine in Dovecot before 2.3.15 allows Uncontrolled Resource Consumption, as demonstrated by a situation with a complex regular expression for the regex extension.

An issue has been discovered in GitLab EE affecting all versions from 15.11 prior to 16.2.2 which allows an attacker to spike the resource consumption resulting in DoS.