An issue was discovered in systemd 253. An attacker can modify the contents of past events in a sealed log file and then adjust the file such that checking the integrity shows no error, despite modifications. NOTE: the vendor reportedly sent "a reply denying that any of the finding was a security vulnerability."
https://github.com/systemd/systemd/releases
https://github.com/systemd/systemd/pull/28885
https://github.com/kastel-security/Journald/blob/main/journald-publication.pdf