An issue has been identified with how Adobe Analytics currently handles Firefox 28's user agent string. Right now Firefox 28's browser ID written to the data tables does not match the lookup ID used in reporting. Because of this, the 'None' line item in the Browsers report groups all current Firefox 28 users into it.
Based on the current circumstances at hand, we will be able to rescue the data from the 'None' line item, but will not be able to group it with the corrected data moving forward. Because of this, you will see two Firefox 28 line items once the fix is in place:
I do not have an ETA on when this fix will go live, but I will be updating this thread as I get more information. Thanks!
Got an update on the bug, engineering is shooting for an EU in the next couple weeks. It will most likely be outside the monthly maintenance release cycle due to the high impact it has.
We have fixed the bad values on the backend - you should see Firefox 28 values since the beginning of this month. We are still working on getting the pre-May 1st FF28 hits out of the None bucket; still not ETA on that one.