Circle Jerks have also recorded a cover of Descendents' "Loser"

Circle Jerks and Descendents are on tour right now. As part of the tour, the bands released a split EP that finds Descendents covering three Circle Jerks songs and Circle Jerks covering Descendents' "Kabuki Girl" and "hope."
Circle Jerks' Keith Morris recently appeared on the vinyl guide podcast. As part of that interview, Keith mentioned that Circle Jerks also recorded a cover of descendents' "Loser" (at Tim Armstrong's studio). According to Keith, he changed some lyrics which might cause controversy, but Bill Stevenson of Descendents asked the band not to include it on the release in order to avoid any chance of controversy. You can also hear Keith Morris whizz during the interview, which you can hear at the link. As of now, there are no plans to release the recording.