Play With Docker vulnerable to Authorization Bypass Through User-Controlled Key

Play With Docker is a browser-based Docker playground. Versions 0.0.2 and prior are vulnerable to domain hijacking.

Because CORS configuration was not correct, an attacker could use `play-with-docker.com` as an example and set the origin header in an http request as `evil-play-with-docker.com`. The domain would echo in response header, which successfully bypassed the CORS policy and retrieved basic user information. This issue has been fixed in commit ed82247c9ab7990ad76ec2bf1498c2b2830b6f1a. There are no known workarounds.