Improper Access Control
An issue was discovered in Project Jupyter JupyterHub OAuthenticator 0.6.x before 0.6.2 and 0.7.x before 0.7.3. When using JupyterHub with GitLab group whitelisting for access control, group membership was not checked correctly, allowing members not in the whitelisted groups to create accounts on the Hub. (Users were not allowed to access other users' accounts, but could create their own accounts on the Hub linked to their GitLab account. GitLab authentication not using gitlab_group_whitelist is unaffected. No other Authenticators are affected.)
CWE-284 - Improper Access Control
Listed 5th in the 'OWASP Top Ten', improper (or broken) access control attacks are a fundamental type of vulnerability. This includes a broad range of design flaws that enable users to act outside of their intended permissions. They can use these privileges to gain access to restricted files and functionality such as accessing restricted information, falsifying records, destroying data, or executing commands.