updated 02:00 pm EDT, Wed March 23, 2011
Suggests minimal changes
A claim of hands-on time with iOS 4.3.1 appears to support the firmware's existence. BGR explains that an "Apple connect" recently installed a pre-release copy on an office iPhone, and that the site has actually been trying out v4.3.1 for the past two days. The code so far only seems to make bugfixes, as anticipated, BGR writes.
One observed difference is that the firmware may improve battery life, which v4.3 wrecked for some device owners. The source of the leak meanwhile adds that people should still expect to see v4.3.1 go live within one to two weeks. Some rumored changes include anti-jailbreaking measures and a fix for the gyroscope going undetected on the iPad 2.