MultiJuicer: Login CSRF allows attacker to force victims into their team

Summary

MultiJuicer is used to run separate Juice Shop instances on a central kubernetes cluster without the need for local instances. In versions 8.0.0 through 10.0.0, the team join endpoint (POST /multi-juicer/api/teams/{team}/join) accepted requests with any Content-Type, including text/plain. Because that content type does not trigger a CORS preflight, an attacker could host a cross-site HTML form that auto-submits to the endpoint and forces a victim's browser to log in as the attacker's team. A successful, undetected attacker can cause victims to unwittingly solve Juice Shop challenges under the attacker's team identity. In a CTF context this lets the attacker inflate their team's score using other players' activity, and any sensitive data the victim enters into "their" Juice Shop ends up in the attacker's instance. The vulnerability is exploitable without any prior authentication; the victim only needs to visit a page the attacker controls while having network access to the MultiJuicer deployment. SameSite=Strict on the session cookie does not mitigate this, because the attack plants a new cookie rather than relying on an existing one. This issue was fixed in version 10.0.1.