Google has posted new factory images for build LMY48I, which contains fixes for the Stagefright security exploit, for several Nexus devices. In all, the new build is available for the Nexus 6, Nexus 9 (LTE and WiFi), Nexus 5, Nexus 7 (2013, WiFi), Nexus 10, and Nexus 4.
Google said the update would roll out today in a blog post announcing a new monthly security update schedule for Nexus devices, and the build number lines up with what Sprint said would begin rolling out to the Nexus 5 and Nexus 6.
If you're interested in manually updating your Nexus device to the latest build, you'll find links from Google for each device receiving LMY48I at the link below. Also be sure to check out our guide to the process, as it's more complicated than simply receiving an OTA update.