Microsoft has begun rolling out an over-the-air update to all Windows 10 Mobile devices with the version number of 10586.545



From Windows Central:

Again, this update is meant to fix some bugs in Windows 10 Mobile. As we previously reported, the big Anniversary Update for the mobile OS is stil due for release sometime "in the coming weeks" but does not yet have a firm date.

  New Windows 10 Mobile cumulative update 10586.545 begins rolling out