Parse Server has a protected fields bypass via LiveQuery subscription WHERE clause

Impact

An attacker can exploit LiveQuery subscriptions to infer the values of protected fields without directly receiving them. By subscribing with a WHERE clause that references a protected field (including via dot-notation or $regex), the attacker can observe whether LiveQuery events are delivered for matching objects. This creates a boolean oracle that leaks protected field values. The attack affects any class that has both protectedFields configured in Class-Level Permissions and LiveQuery enabled.

Patches

The fix adds validation of the LiveQuery subscription WHERE clause against the class's protected fields, mirroring the existing REST API validation. If a subscription's WHERE clause references a protected field directly, via dot-notation, or inside $or / $and / $nor operators, the subscription is rejected with a permission error. This is applied during subscription creation, so existing event delivery paths are not affected.

Workarounds

Disable LiveQuery for classes that use protectedFields in their Class-Level Permissions, or remove protectedFields from classes that require LiveQuery.

References

• GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-j7mm-f4rv-6q6q
• Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.6.0-alpha.9
• Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.35