react-qrcode-logo VS CyberChef

Adding logos to QR codes, changing colors or replacing squares with circles in QR code is a CS sophomore weekend project at best. It's really fun and quite easy to do. You don't even need to understand Reed-Solomon codes for that.

This project, however, didn't even implement it. It just imports popular react library `react-qrcode-logo` [1] which does all the job (few dozens lines, really) [2].

[1] https://www.npmjs.com/package/react-qrcode-logo

[2] https://github.com/gcoro/react-qrcode-logo/blob/master/lib/i...

Are you familiar with coding? A simple web page with React and https://github.com/gcoro/react-qrcode-logo is pretty trivial to do, maybe you can even start a project to do something like snippetbox does but with QRs

Then we take the encrypted text and use CyberChef to decrypt it.

Let's go to CyberChef and insert our pieces of evidence.

A parameter was changed from '2AMBCgIQBg' to 'CgIIAdgDAQ%3D%3D' which is just the correct base64 encoding they should have been using the entire time.

I don't think this was a hostile action by Google, I think someone just added better input validation for security reasons and it accidently broke the bad requests they were sending.

https://gchq.github.io/CyberChef/#recipe=URL_Decode()From_Ba...

❗This is indeed the flag, but the text is encrypted with Base64. Usually, the presence of padding character "=" indicates that's Base64 type of encoding (but that's only one of the hints). To decrypt it, we can use CyberChef. Copy-paste the text and we either:

It uses a combination of magic bytes (like the `file` command), entropy analysis and character frequency detection to determine whether an output is likely to be of interest to the user.

The file type mechanism is written here[0]. There's a list of all signatures we detect here[1].

[0] https://github.com/gchq/CyberChef/blob/master/src/core/lib/F...

I think this can be deciphered using CyberChef...