Guess my password (robbers' thread) Inspired by this challenge, which got closed. This is meant to be an easier, but no less interesting version of that.
This is the robbers thread of a cops-and-robbers challenge. For the cops thread, see here.
Cops will provide a program/function and a flag. Robbers will guess a password. When the password is given to the cop's program, the flag should be outputted.
Robber rules

When the cop's program is given the password you guess, it should output the flag.
Your password does not have to be the same as the cop's password.
You are allowed to take advantage of ambiguous descriptions of the flag by cops.

Cop answers will be safe if they haven't been cracked for two weeks.
Example
Cop:
Scala, 4 bytes
x=&gt;x

Flag: Yay, you cracked it! (an object of type String is returned from the lambda above)
Try it online!
Robber:
Password: the string &quot;Yay, you cracked it!&quot;
Try it online!
Sisyphus, PHP
Password:
A string golf with 1,000,000 leading whitespaces and 1,000,000 trailing whitespaces
Output: golf
Reason: 1,000,000 is the default backtracking limit of PCRE (which you can get by var_dump(ini_get('pcre.backtrack_limit'));). And preg_match will return FALSE other than 0 or 1 when this limit is breaked.
Try it online!