If you’ve got an AT&T-locked iPhone and have plugged it into iTunes anytime in the past few hours, you may have noticed a dialog box pop up with the following:
“An update to the carrier settings for your iPhone is available. Would you like to download it now?”
.. And that’s it. No patch notes, no sign of what said update would actually do. Always inquisitive, we went ahead and pulled the trigger – then got to sleuthing.
After splaying open the update package and looking too hard at a whole bunch of stuff that appeared to be exactly the same as it had always been, we finally spotted them sitting in plain sight: “Default_CARRIER_ATT M-Cell.PNG” and “FSO_CARRIER_ATT M-Cell.PNG”. What might these mystery images contain? A map to Atlantis, perhaps?
Sadly, no. It was just this: 
Two images, both saying just “AT&T M-Cell”, one in a light font, the other dark. They’re just carrier logo replacements for AT&T’s upcoming cell-tower-in-your-living-room MicroCell – when you’re connected to the MicroCell (or M-Cell, apparently), it’ll show these logos up at the top instead of the default AT&T ones.
Pint-sized mystery solved!