Samsung's Galaxy S5 and HTC's One M9 are both wonderful devices given their age, and those still rocking them on Verizon's network just got an update that brings them up to the latest Android security patch level, along with a small tweak for the Galaxy S5's handling of email. Galaxy S5 users who take advantage of Microsoft Outlook compatibility found that they were unable to download attachments in Outlook 2003 or Outlook 2007. This update fixes that bug, and brings the phone up to par on its monthly security patches. The device is still stuck on Android 6.0 (Marshmallow), of course. The HTC One M9 gets no such handy fixes, however, getting only the new security patch; like the Galaxy S5, HTC's 2015 flagship is stuck on Marshmallow for now, and Verizon has announced no plans to adopt the Nougat update that HTC has rolled out to unlocked One M9 units.
The security update being rolled out to both phones in these updates is the April patch, which hit Nexus and Pixel phones at the beginning of the month, and has also made its way to a few more recent flagship devices. The patch in question was fairly run of the mill, aside from patching up a pretty severe remote code execution vulnerability that could be exploited through a wide range of means, such as email, web browser code, and even MMS messages.
Users who are averse to rooting shouldn't let these updates get their hopes up; Verizon has been slow to roll out some updates in the past, and they've made no indication of any interest in bringing either phone up to Nougat, despite HTC putting out a Nougat software version for unlocked One M9 units. Samsung, meanwhile, has shown few signs of life regarding the Galaxy S5, which likely means that all US versions of it will remain on Marshmallow indefinitely. While both phones can get on the latest version of Android through custom ROMs, that solution is not exactly for the faint of heart, given Verizon's penchant for locking down bootloaders and generally making their devices harder to modify than most other carrier variants.