Not just rumor! MIT proves this with every new release. I haven't followed it since Vista Ultimate 64 (so I dunno about Win7 - I'm SURE it's the same thing!). It started with Win95 IIRC. Microsoft even admitted it for one of their OS's - I forget which. This is very common knowledge in real security circles in academia. I doubt Charlie Miller (LOL!!!) would have a clue. According to MIT the backdoors take on several different forms - some more detectable than others.
You can easily verify this yourself just by searching in Google. So unless your browser is busted or something don't waste my time asking for proof and details. Rather just type in something like: "government backdoor in Microsoft windows" or "NSA backdoor in Windows" and read it for yourself.
http://www.google.com/search?client...ckdoor+in+Microsoft+windows&ie=UTF-8&oe=UTF-8
http://www.google.com/search?hl=en&...A+backdoor+in+Microsoft+windows&aq=f&oq=&aqi=
http://www.linuxtoday.com/news_story.php3?ltsn=1999-09-03-007-10-SC
etc. etc. etc.
.
I'm sure MS would prefer everyone to be arguing conspiracy theories (which are ultimately very hard to back up with actual PROOF) rather than discussing the more damning things which we know actually happened in the real world. Like the multiple lawsuits regarding the theft of intellectual property from smaller developers, all resulting in gag orders.
Even discussing this diverts discussion away from the abhorrent trainwreck that was Windows Vista - which Microsoft desperately want us to forget about.