Persistent privilege escalation via unverified compilation artifacts

Improper artifact validation in Android 12 allows local users with System execution privileges to persist privileged code across reboots. Odsign in odsign_main.cpp calls odrefresh --compile before verifying existing artifacts, so partial compilation can retain attacker-written files not protected by fs-verity. Exploitation requires prior System-level filesystem compromise; no user interaction is required, and the consequence is persistent privileged execution.