Speckle Server API Token Privilege Escalation

QFinch assessment

Speckle Server provides server, frontend, 3D viewer, and other JavaScript utilities for the Speckle 3D data platform. A vulnerability in versions prior to 2.17.6 affects users who: authorized an application which requested a 'token write' scope or, using frontend-2, created a Personal Access Token (PAT) with `token write` scope. When creating a new token an agent needs to authorise the request with an existing token (the 'requesting token'). The requesting token is required to have token write scope in order to generate new tokens. However, Speckle server was not verifying that other privileges granted to the new token were not in excess of the privileges of the requesting token. A malicious actor could use a token with only token write scope to subsequently generate further tokens with additional privileges. These privileges would only grant privileges up to the existing privileges of the user. This vulnerability cannot be used to escalate a user's privileges or grant privileges on behalf of other users.