Windows Phone 8.1 being tested, according to AdDuplex data

A tweet from Alan Mendelevich from mobile ad network AdDuplex reveals thatWindows Phone 8.1 testing has appeared on the network.
Mendelevich calls this a final tease before AdDuplex's May report. According to the data, the new build of Microsoft's mobile OS has been seen on the Nokia P4301 test device as well as on the HTC 8X and the Nokia Lumia 920.While Windows Phone 8.1 is rumored to be the new Blue version of Windows Phone featuring IE11, it also could be the minor GDR2 update that also is expected. Back in March, we brought to your attention a job posting for Microsoft seeking a test engineer for Windows Phone 9 which is a separate project than Windows Phone Blue. The latter is more about merging different variants of Windows. Last month, speculation had Windows Phone 9 launching in October.