There are many, many unpatched vulnerabilities on Motorola Milestone XT720 (and many others). Google doesn't even release security patches for old releases (until recently)--their opinion seems to be that all manufacturers should update to Gingerbread or whatever the latest OS happens to be. Google finally seems to have pulled their heads out of the sand or stopped humming with their fingers in their ears recently and made security point release for Froyo a few weeks ago that backported some security fixes that had been in Gingerbread for a long time, though.