Ruby OpenID (aka ruby-openid) through 2.8.0 has a remotely exploitable flaw. This library is used by Rails web applications to integrate with OpenID Providers. Severity can range from medium to critical, depending on how a web application developer chose to employ the ruby-openid library. Developers who based their OpenID integration heavily on the "example app" provided by the project are at highest risk.
https://security.gentoo.org/glsa/202003-09
https://marc.info/?l=openid-security&m=155154717027534&w=2
https://lists.debian.org/debian-lts-announce/2019/10/msg00014.html