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

Analyze the memory-string record `memdump.txt` to recover the executed command history. Decode the Base64 strings and read the flag from the arguments of the suspicious command piped into bash.
Extract long base64-looking strings from memdump.txt
The line piping a decoded blob into bash is the attacker command
The flag is near that command's arguments