CVE-2022-39385: Users erroneously and transparently added to private messages in Discourse

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-11-14 · updated 2026-06-17
Weakness: CWE-200

Description

Discourse is the an open source discussion platform. In some rare cases users redeeming an invitation can be added as a participant to several private message topics that they should not be added to. They are not notified of this, it happens transparently in the background. This issue has been resolved in commit `a414520742` and will be included in future releases. Users are advised to upgrade. Users are also advised to set `SiteSetting.max_invites_per_day` to 0 until the patch is installed.

Affected products

discourse: before 2.8.10; 2.9.0-beta1, 2.9.0-beta10, 2.9.0-beta2, 2.9.0-beta3, 2.9.0-beta4, 2.9.0-beta5 (+3) — fixed in 2.8.10

How to fix

Upgrade to a fixed version: discourse 2.8.10. Check the vendor advisory for mitigations.

References

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