Rating:

1. Find the shit ton of weird looking files (``mercury/.hg/store/data/``)

2. Observe that all of them occupy 66 bytes except one
![Screenshot](ss1.png)

3. Open the outlyer and extract the flag

![Screenshot](ss2.png)

Original writeup (https://github.com/TrollzorFTW/writeups/tree/master/bsidesbos/forensics/mercury).