Decidim vulnerable to sensitive data disclosure

Note: added the actual report as a comment.

Summary

Decidim, a platform for digital citizen participation, uses a third-party library named Ransack for filtering certain database collections (e.g., public meetings). By default, this library allows filtering on all data attributes and associations. This allows an unauthenticated remote attacker to exfiltrate non-public data from the underlying database of a Decidim instance (e.g., exfiltrating data from the user table).

Impact

This issue may lead to Sensitive Data Disclosure.

Patches

The problem was patched in v0.27.3.

Workarounds

Disable or unpublish all meetings components from your application.