Same thing in Firefox as Chromium, this is an issue with the sanitized helper profile
Apr 26 14:29:18 sec-precise-i386 kernel: [ 6213.328525] type=1400 audit(1335468558.190:46): apparmor="DENIED" operation="exec" parent=20292 profile="/usr/lib/firefox/firefox{,*[^s][^h]}//sanitized_helper" name="/usr/share/software-center/piston_generic_helper.py" pid=20300 comm="software-center" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0
Same thing in Firefox as Chromium, this is an issue with the sanitized helper profile
Apr 26 14:29:18 sec-precise-i386 kernel: [ 6213.328525] type=1400 audit(133546855 8.190:46) : apparmor="DENIED" operation="exec" parent=20292 profile= "/usr/lib/ firefox/ firefox{ ,*[^s][ ^h]}//sanitized _helper" name="/ usr/share/ software- center/ piston_ generic_ helper. py" pid=20300 comm="software- center" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0