On the website we don't find the flag, but regarding the Challange descption, it should have been there in the past. So we use the [wayback machine](https://archive.org/web/) to look at a saved state of this website and we discover one savepoint from April 18, 2020. Using that we find the blogpost "Challenge Accepted!" which didn't appear before which contains the link to the flag:
[https://web.archive.org/web/20200418213402/https://apporima.com/flag.txt](https://web.archive.org/web/20200418213402/https://apporima.com/flag.txt)

JCTF{the_wayback_machine}