Parse Server session creation endpoint allows overwriting server-generated session fields

Impact

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 server's session expiration policy by setting an arbitrary far-future expiration date. It also allows setting a predictable session token value.

Patches

The session creation endpoint now filters out server-generated fields from user-supplied data, preventing them from being overwritten.

Workarounds

Add a beforeSave trigger on the _Session class to validate and reject or strip any user-supplied values for sessionToken, expiresAt, and createdWith.