https://meashiri.github.io/ctf-writeups/posts/202312-backdoorctf/#forenscript

TLDR: Two layers to this problem.
1. The given binary data is a PNG file with every 4 bytes flipped in order.
2. Once the order is corrected, we can see that there is a second PNG file attached to the end of the first red herring PNG. Extract the second image to get the flag.

```bash
% xxd -c4 -p a.bin | sed -E 's/(..)(..)(..)(..)/\4\3\2\1/g' | tr -d '\n' | xxd -r -p | dd skip=60048 of=b.png ibs=1
# open b.png and get the flag
```

Original writeup (https://meashiri.github.io/ctf-writeups/posts/202312-backdoorctf/#forenscript).