This flaw allows any authenticated user - regardless of their assigned role - to access or modify restricted upload collections. An attacker can read the content of protected upload documents and overwrite critical fields like alt and keywords. The vulnerability is critical for environments that rely on Payload's access control features to manage document permissions. The impact is categorized as an Incorrect Authorization (CWE-863) issue.

Attack Chain

1. Attacker establishes a valid, low-privileged user session within the Payload CMS environment.
2. Attacker identifies a target upload collection that is meant to be restricted to administrative roles.
3. Attacker crafts a POST request targeting the plugin's /api/alt-text-plugin/generate or /bulk endpoints.
4. Attacker includes specific JSON parameters (id, collection, locale) to target a protected document.
5. The plugin receives the request and executes a Payload Local API call without setting overrideAccess: false.
6. Payload CMS internal logic defaults overrideAccess to true, bypassing all defined read or update access control functions for the collection.
7. The plugin reads or modifies the protected alt and keywords fields on behalf of the attacker.
8. Attacker successfully exfiltrates data or alters metadata in documents they are not authorized to access.

Impact

The vulnerability allows unauthorized read/write access to sensitive metadata within restricted upload collections. An attacker can modify alt text and keywords for any document, potentially poisoning content, bypassing organizational access policies, or exfiltrating document metadata that should be restricted based on user role assignments.

Recommendation

Prioritize the upgrade of @jhb.software/payload-alt-text-plugin to version 0.7.1 or later, where the overrideAccess parameter is correctly set. For teams unable to patch immediately, implement a custom server-side guard to validate that the req.user role has the necessary permissions for the target collection before the request reaches the plugin handler.