Plane is an open-source project management tool. Prior to 1.4.0, Plane trusts email addresses returned by Gitea OAuth and by self-managed GitLab OAuth deployments where email confirmation is disabled, without verifying that the provider authenticated ownership of the address. An attacker can set an OAuth identity's unverified provider email to a victim's address, which Plane matches directly to the victim's existing local account. The attacker can then log in to the victim's Plane account without knowing the victim's password. GitHub, GitLab.com, and Google are not affected because those providers return verified email addresses. This issue is fixed in 1.4.0.