> JPEG compression causes ringing artifacts that can extend out past the pixels you're trying to redact, up to the next block boundary. This. I made a respons

> JPEG compression causes ringing artifacts that can extend out past the pixels you're trying to redact, up to the next block boundary. This. I made a response to the parent question that goes into the practical side of this in a bit more detail, but this is a much better one-sentence summary of /how/ the information leaks.