CVE-2022-24866 is a medium-severity vulnerability affecting the discourse-assign plugin, a component used within the Discourse open-source messaging platform. The vulnerability arises from the UserBookmarkSerializer serializing the entire User and Group objects prior to version 1.0.1. This serialization process inadvertently exposed sensitive private information. By default, the serialized data was only accessible to staff members who have permission to view assignment information, limiting exposure to trusted personnel. However, in configurations where the assign feature was enabled publicly, this sensitive data could be accessed by a broader set of users beyond staff, increasing the risk of unauthorized information disclosure. The vulnerability is classified under CWE-200, which pertains to the exposure of sensitive information to unauthorized actors. The issue was addressed in version 1.0.1 of the discourse-assign plugin, which introduced a patch to restrict serialization to only the necessary data. There are currently no known exploits in the wild, and no alternative workarounds have been identified apart from upgrading to the patched version. The vulnerability does not require user interaction or authentication beyond the existing permission model, but the risk depends heavily on how the assign feature is configured on the affected Discourse instance. Since Discourse is widely used for community discussions, forums, and internal communications, the exposure of user and group data could lead to privacy violations, social engineering opportunities, or unauthorized insight into organizational structures.

For European organizations using Discourse with the discourse-assign plugin, this vulnerability could lead to unauthorized disclosure of sensitive user and group information. While the default configuration limits exposure to staff members, any misconfiguration enabling public access to assignment features significantly raises the risk. Potential impacts include privacy breaches under GDPR regulations, reputational damage, and increased susceptibility to targeted phishing or social engineering attacks leveraging leaked user data. Organizations with public-facing Discourse forums or those using the assign feature for broader user groups are particularly vulnerable. The exposure of internal group structures or user details could also aid adversaries in mapping organizational hierarchies or identifying privileged users, which may facilitate further attacks. Although no active exploitation has been reported, the presence of this vulnerability in widely deployed open-source software used by European public sector entities, educational institutions, and private enterprises underscores the need for prompt remediation to maintain compliance and security posture.

1. Immediate upgrade to discourse-assign plugin version 1.0.1 or later to apply the official patch that restricts serialization to necessary data only. 2. Audit current Discourse configurations to verify that the assign feature is not publicly accessible unless explicitly required. Restrict assignment viewing permissions strictly to trusted staff members. 3. Conduct a review of user and group data exposure within Discourse instances to identify any inadvertent leaks. 4. Implement monitoring and alerting for unusual access patterns to assignment information or user/group data within Discourse logs. 5. Educate administrators on secure configuration best practices for Discourse plugins, emphasizing the principle of least privilege. 6. For organizations with public-facing Discourse instances, consider additional access controls such as IP whitelisting or VPN requirements for sensitive features. 7. Regularly review and update Discourse and its plugins to incorporate security patches promptly. 8. If upgrading immediately is not feasible, restrict network access to Discourse instances hosting the vulnerable plugin to trusted internal networks until patched.