Flatpack-522.rar -

hidden.txt now contains:

Good luck, and happy hunting!

[LSB] bpp: 8, plane: 0, offset: 0, bits: 1, 0x30 bytes hidden (ASCII) Extract the LSB stream:

The secret lies within the binary. So the PNG is just a hint, not the flag itself. 6.1 File Type $ file mystery.bin mystery.bin: data Run binwalk to look for embedded files: flatpack-522.rar

$ zsteg -a cover.png Output shows:

Try the following candidates:

# 2. Extract inner archive (no password) unrar x inner.rar hidden

Cannot open encrypted file. Use -p option to specify a password. Thus we need the password. 3.1 Brute‑Force / Dictionary Attempts A quick dictionary attack with common passwords (e.g., password , 12345 , admin ) fails. The creator hints in the challenge description: “The key is hidden inside the name of the pack itself.” The file name flatpack‑522 suggests the password may be related to the number 522 .

DECIMAL HEX DESCRIPTION 0 0x0 PNG image, 256 x 256, 8-bit/color RGBA, non-interlaced Extract the PNG:

# 1. Extract outer archive (password = 522) unrar x -p522 flatpack-522.rar Thus we need the password

$ zbarimg _mystery.bin.extracted/00000000.png QR-Code:HTBfl4t_p4ck_5c4nn3r_2023 That is the flag. Below is a one‑liner script that reproduces the entire process automatically. It assumes you have unrar , zsteg , binwalk , and zbarimg installed.

$ steghide extract -sf cover.png -p "" -xf hidden.txt (If steghide asks for a password, just press Enter – it’s not password protected.)

$ display cover.png Nothing obvious appears. However, the challenge name “FlatPack” hints at “flat” data (i.e., a flat image with hidden data). Use zsteg (a popular stego tool) to search for hidden data: