Unauthorized Subscription Creation to Confluence Space in Mattermost Confluence Plugin

Vulnerability

Overview

The Mattermost Confluence Plugin prior to version 1.5.0 does not verify whether the requesting user has access to the target Confluence space when creating a subscription. This missing authorization check at the plugin's create subscription endpoint allows any authenticated user to subscribe to events (such as page updates, comments, and space changes) from any Confluence space, regardless of their actual permissions in Confluence [1][2].

Exploitation

To exploit this vulnerability, an attacker must be an authenticated user in Mattermost and have the ability to invoke the plugin's subscription creation command. No special privileges within Mattermost or Confluence are required beyond basic authentication. The plugin's subscription functionality triggers on specified Confluence events (e.g., page created, updated, commented) and sends notifications to a designated Mattermost channel. By creating a subscription to a space the user cannot access, the attacker can receive information about events they otherwise would not see [2].

Impact

A successful exploit allows the attacker to monitor activity in Confluence spaces they are not authorized to view. This results in unauthorized information disclosure of Confluence events, which may include sensitive content such as new page titles, change summaries, or comment snippets. The exposed data could aid in further attacks or violate data confidentiality policies. No account takeover or code execution is involved; the impact is limited to observing space events without direct read access to the full content [1][2].

Mitigation

Users should upgrade to Mattermost Confluence Plugin version 1.5.0 or later, which includes the necessary access control checks when creating subscriptions. No workaround is available, as the fix requires code changes in the plugin. As of the publication date, the vendor has addressed this vulnerability in the patched version [1][3].