I think it was just overly aggressive settings of compression parameters. I don't see any evidence that the jbig2 compressor was implemented incorrectly. Source: [1]
[1]: https://www.xerox.com/assets/pdf/ScanningQAincludingAppendix...
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Right. Jbig2 supports lossless compression. I'm not very familiar with the bug, but it could have been a setting somewhere in the scanner/copier that it was changed to lossy compression instead. Or they had lossy compression on by default or misconfigured some other way (probably a bad idea for text documents).
The bad thing was that it used lossy compression when copying. That was the problem.
No. The bug was when using the "Scan to PDF" function. It happened on all quality settings. Copying (scanning+printing in one step, no PDF) was not effected.
I remember differently, but I don't want to pull up the source right now.
I did check some of the sources, but was not able to find the one I remember which had statistics on it.
The xerox FAQ to it does lead me to consider that I might be confusing this with some other incident though, as they claim that Scanning is the only thing that is affected.
https://media.ccc.de/v/31c3_-_6558_-_de_-_saal_g_-_201412282...
I'd believe him more then any other source.
He did his presentation in english at FrOSCon 2015, can be seen here: https://www.youtube.com/watch?time_continue=95&v=c0O6UXrOZJo