Here's an OxygenOS 1.0.2 update for your OnePlus One containing patches for the recent "Stagefright" security exploit. "Stagefright" is basically a vulnerability in the multimedia stack that can be exploited via MMS which could compromise your phone. If you are currently using OxygenOS, I would highly recommend upgrading to this version for your own safety.
Again, before flashing, please backup all your data just to be safe.
If you are already on OxygenOS, this update does not require a reset.
For detailed installation guide, you can find it here
***** UPDATE 8/19 *****
Google has released a couple more patches for Stagefright which we will be incorporating over the next few days. We are anticipating another rollout before the end of next week. Stay tuned.