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

fuzz-results.log is generated from the FLAG injected at startup. Select the SIGSEGV input and XOR-decrypt it with BLAKE2s(fuzz-case-17) to recover the flag.
Inspect fuzz-results.log and identify the target record
select the SIGSEGV input and XOR-decrypt it with BLAKE2s(fuzz-case-17)
Verify that the reconstructed value has FLAG{...} format