Comment 7 for bug 123365

I've found out that it affects feisty too, if you have p7zip installed (which my brother's pc didn't). If you have a feisty livecd or vm or something, you can do this:
Fire up the livecd/vm. Add universe (and perhaps multiverse, I'm not sure) repos to sources.list. Install p7zip (sudo aptitude update ; sudo aptitude install p7zip) and then try to add some files/a file to an archive. Look at the formats. At the bottom are two 7z's. Make exactly the same archive but using the two different 7z's. Now check the sizes. Exactly the same. Now do a diff (diif archive1.7z archive2.7z). No differences. Now md5sum them both (md5sum archive1.7z archive2.7z). Exactly the same md5.

I'll test this on earlier ubuntu versions when I have time.