Rumored to be something between a Jelly Bean and a slice of Key Lime Pie, Android 4.3 is currently appearing in search results on the Android developers' site.
Numerous excerpts in the results reference "Security Enhancements in Android 4.3"
Click through any of those results and you'll find a page with no apparent mentions of the new Android update, although it is hidden in the HTML. Click through the link in that tag and you get a 404. Dead end. Scavenger hunt over.
Guess we have to wait for the expected unveil of the update during the Google I/O keynote, which you can conveniently follow here on CNET.
Hat tip to The Verge.