It is entirely possible that they did, indeed, halt a plot, just as they said they did.
Not it fucking isn't.
The NSA says it closed this vulnerability by working with computer manufacturers.
Where are motherboards and BIOS shit is fucking manufactured / written? (Hint: China and Taiwan)
Do you really think it's possible that a BIOS update was created by those manufacturers that:
1: Applied to all the vulnerable systems, many of which are 10+ years old and manufactured by a now defunct-company
3: Got deployed
4: Had all of the above happen with no one knowing about it outside of the NSA, the manufacturers, and the one guy in the world who writes BIOS patch notes
Hell, I'll GIVE you the fucking BIOS patch notes.
BIOS Version 2.3.5
1 - Updated tables to half-support new Intel processors. Buy a new motherboard with new socket if you want it to actually work, though.
2 - Updated Intel Option ROM. Just kidding, we're not updating that anymore, this motherboard has been out for 2 months already.
3 - Various menu items have been slightly changed, and some of your settings will be wiped, we won't document which or why, though.
At least this shit is believable.