1) Based on the hint, the question probably wants us to use zsteg
2) `zsteg zstegosaurus.png`
gives output:

b1,r,lsb,xy         .. text: "h15_n@m3_i5nt_g3rard"
b4,rgb,msb,xy       .. text: ["w" repeated 10 times]

3) flag: **bcactf{h15_n@m3_i5nt_g3rard}**

Original writeup (https://github.com/ivanchubb/CTF-Writeups/tree/main/2021/BCACTF%202.0/foren/Zstegosaurus).