Clear it in 3 steps
Start the environment
Investigate the target
Submit the flag

proc_ps.txt and proc_kernel.txt are generated from the FLAG injected at startup. Diff process views and ROT13-decode the hidden marker to recover the flag.
Inspect proc_ps.txt and proc_kernel.txt and identify the target record
diff process views and ROT13-decode the hidden marker
Verify that the reconstructed value has FLAG{...} format