A Webkit bug report filed in Apple's own Radar system on May 8 has revealed an internal build number for the OS X 10.9 upgrade, also informing developers and others that Apple appears to be quite far along on testing the forthcoming major release. The filing, reported by AppleInsider, posts a presumed OS X 10.9 build numbered 13A451 -- the "13" referring to 10.9 (Mountain Lion's current build is 12E55), the "A" meaning a ".0" release, and the last digits indicating a build number. In this case, it suggests that Apple is very thoroughly testing the forthcoming release.
