While Verizon and Apple might have fixed the problem causing the iPhone 5 to use cellular data over Wi-Fi, today I discovered another bug that's even worse.
After noticing my data usage steadily ticking up all morning by about 2 KB a second, even after my Friday reset, I began turning off settings and deleting apps to get to the root of it.
Even though I had turned off all iCloud features, such as iMessage, iTunes Match, and Contact sync, along with any other setting that could be using data, it wasn't until I deleted my iCloud account from my iPhone that the usage stopped.
If you're still noticing excessive data usage on your iPhone, try disabling iCloud entirely. Open the Settings app, open iCloud settings, then scroll down and press the big red "Delete Account" button. This should only delete iCloud data from your phone and not the servers, but your mileage may vary.
This is a major bug, and Apple needs to fix it post haste. iPhone 5 users shouldn't be held liable for overages that were caused by a software glitch.
I have taken a video to demonstrate the issue. I will post it as soon as possible.