JSON Options <= 0.0.4 - Unauthenticated Arbitrary Options Update

The JSON Options WordPress plugin through 0.0.4 does not have any capability check or nonce verification on one of its actions, which runs on every request and is available to unauthenticated users, allowing them to update arbitrary WordPress options. This can be leveraged to enable user registration and set the default role to administrator, leading to privilege escalation and full site takeover.