T-Mobile has begun pushing out an update to both the the Samsung Galaxy Note 4 and Galaxy Note Edge, bringing along a patch for the so-called Stagefright messaging exploit. These appear to be the only two T-Mobile devices receiving the update for now, but we wouldn't expect the Galaxy S6 and S6 Edge to be too far behind.
According to T-Mobile, these updates contain "messaging security improvements" and are available both over the air and via Samsung Kies. Given that Samsung has committed to releasing monthly security updates for its phones going forward, it's good to see carriers working quickly with the manufacturer to get the first of such updates out the door.
Update: You can add another one to the list, as it looks like T-Mobile's Galaxy S5 is receiving the update as well.
Thanks for the tip, Brian!