Rubygems.org is the Ruby community's gem hosting service. Rubygems.org users with MFA enabled would normally be protected from account takeover in the case of email account takeover. However, a workaround on the forgotten password form allows an attacker to bypass the MFA requirement and takeover the account. This vulnerability has been patched in commit 0b3272a.
https://github.com/rubygems/rubygems.org/security/advisories/GHSA-4v23-vj8h-7jp2
https://github.com/rubygems/rubygems.org/commit/0b3272ac17b45748ee0d1867c49867c7deb26565