[CentOS] RHEL/CentOS bugfixing policy for LibreOffice, Firefox, Thunderbird?

Hi,

RHEL/CentOS releases 5.x, 6.x and 7.x are all shipping reasonably recent 
versions of Firefox ESR, Thunderbird ESR and LibreOffice. Until recently 
I've been using Slackware Linux as a base system for client's desktops 
and workstations. Since my primary aim is reliability, I always tried to 
opt for the most stable releases, so for example I'd rather go for 
LibreOffice 4.2.8 than 4.3.1.

A question just crossed my mind: does RHEL include software like 
LibreOffice, Firefox, Thunderbird "as is" from upstream, or is there 
some RHEL-specific quality control and bugfixing for this kind of software?

Cheers,

Niki
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