Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.17 and 8.6.42, an authenticated user can overwrite server-generated session fields (sessionToken, expiresAt, createdWith) when creating a session object via POST /classes/_Session. This allows bypassing the servers session expiration policy by setting an arbitrary far-future expiration date. It also allows setting a predictable session token value. Starting in version 9.6.0-alpha.17 and 8.6.42, the session creation endpoint filters out server-generated fields from user-supplied data, preventing them from being overwritten. As a workaround, add a beforeSave trigger on the _Session class to validate and reject or strip any user-supplied values for sessionToken, expiresAt, and createdWith.
Weakness
The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.
Extended Description
If the object contains attributes that were only intended for internal use, then their unexpected modification could lead to a vulnerability. This weakness is sometimes known by the language-specific mechanisms that make it possible, such as mass assignment, autobinding, or object injection.
Potential Mitigations
- If available, use features of the language or framework that allow specification of allowlists of attributes or fields that are allowed to be modified. If possible, prefer allowlists over denylists.
- For applications written with Ruby on Rails, use the attr_accessible (allowlist) or attr_protected (denylist) macros in each class that may be used in mass assignment.