TBB-Firefox leaks the OS and kernel version to Mozilla update servers
‘echelon’ also reports that TBB-Firefox sends the OS and kernel version when he/she/it opens the ‘About TorBrowser’ dialog:
2012-08-30 01:56:53 <echelon> https://aus3.mozilla.org/update/3/Firefox/10.0.5/20120608001639/Linux_x86-gcc3/en-US/default/Linux%202.6.37.6-smp%20(GTK%202.24.4)/default/default/update.xml?force=1
(It probably shouldn't be connecting to that server at all, because an update package containing an unpatched Firefox would make TBB completely unsafe.)