Post-patch forensics is the examination of logs, files, processes, and other system activity after a vulnerability has been fixed. Its purpose is to determine whether an attacker exploited the weakness before remediation. Installing a patch closes the known path forward, but does not reveal whether a system was already accessed or altered.
In practice, defenders review evidence from the period when the system was exposed, including authentication and web-server logs, process records, file changes, and runtime behavior. This can help identify suspicious commands, persistence, or data access and guide containment and recovery. Preserve relevant evidence and account for gaps in logging; a clean-looking system or a successful update alone does not prove that compromise did or did not occur.