Despite the woes of OnePlus many years ago, they've done a fantastic job in turning their reputation around and becoming one of the better smartphone manufacturers for software updates. Admittedly, OnePlus hasn't quite managed to meet monthly security updates, but between giving the OnePlus 3/3T an extra Android version and security patches every couple of months, the company is doing better than most. OxygenOS 9.0.10 is now out for the OnePlus 5/5T, and it comes with December 2019 security patches. The most recent stable OxygenOS version for the OnePlus 5/5T contained the October 2019 security patches.

OnePlus 5 XDA Forums || OnePlus 5T XDA Forums

There are no other major changes, apart from general bug fixes and improvements which are always included as a part of OnePlus' update changelogs anyway. The update hasn't been announced on the OnePlus forums yet, but it's already beginning to roll out to users. It's expected to be a staged rollout, where not everyone will get it at once in case there are any problems. If you don't want to wait, you can download the relevant zip package for your device below and manually install it. All you'll need to do is copy the zip file to the root of your phone's storage and then go to settings, system, system updates, and choose "local upgrade."

OxygenOS 9.0.9 to 9.0.10 for the OnePlus 5 || OxygenOS 9.0.10 Full OTA for the OnePlus 5

OxygenOS 9.0.9 to 9.0.10 for the OnePlus 5T || OxygenOS 9.0.10 Full OTA for the OnePlus 5T

For those wondering where Android 10 is, OnePlus has the OnePlus 5/5T slated to receive the update sometime in Q2 of 2020. You can check out the company's roadmap here for when updates are expected to arrive for the OnePlus 6/6T and the OnePlus 5/5T.

Thanks to XDA Senior Member Some_Random_Username for the links!