The auth_internal plugin in Tiny Tiny RSS (aka tt-rss) before 2021-03-12 allows an attacker to log in via the OTP code without a valid password. NOTE: this issue only affected the git master branch for a short time. However, all end users are explicitly directed to use the git master branch in production. Semantic version numbers such as 21.03 appear to exist, but are automatically generated from the year and month. They are not releases.