CVE-2023-23622: Discourse: Presence of read restricted topics may be leaked if tagged with a tag that is visible to all users

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-03-17 · updated 2026-06-17
Weakness: CWE-200

Description

Discourse is an open-source discussion platform. Prior to version 3.0.1 of the `stable` branch and version 3.1.0.beta2 of the `beta` and `tests-passed` branches, the count of topics displayed for a tag is a count of all regular topics regardless of whether the topic is in a read restricted category or not. As a result, any users can technically poll a sensitive tag to determine if a new topic is created in a category which the user does not have excess to. In version 3.0.1 of the `stable` branch and version 3.1.0.beta2 of the `beta` and `tests-passed` branches, the count of topics displayed for a tag defaults to only counting regular topics which are not in read restricted categories. Staff users will continue to see a count of all topics regardless of the topic's category read restrictions.

Affected products

discourse: before 3.0.0; 1.1.0-beta1, 1.1.0-beta2, 1.1.0-beta3, 1.1.0-beta4, 1.1.0-beta5, 1.1.0-beta6 (+200) — fixed in 3.0.0

How to fix

Upgrade to a fixed version: discourse 3.0.0. Check the vendor advisory for mitigations.

References

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