NamelessMC is website software for Minecraft servers. In versions 2.2.4 and prior, the OAuth callback handling does not validate the state parameter server-side before exchanging the authorization code. This allows an attacker to capture a valid OAuth callback URL for their own account and cause a victim's browser to navigate to it, resulting in the victim's session being authenticated as the attacker-linked account (OAuth login CSRF / session swapping). This is patched in version 2.2.5.
CWE-302, CWE-346, CWE-352