https://www.techradar.com/news/oneplus-6-has-a-serious-security-flaw-and-a-fix-is-on-the-way

The OnePlus 6 is a fantastic smartphone, but it also has a pretty serious security flaw, as discovered by an independent security researcher – a flaw that could give tech-savvy hackers unrestricted access to your phone, if they were given physical access to it.

As reported on XDA Developers, and first noticed by researcher Jason Donenfeld of Edge Security, the bootloader on the OnePlus 6 isn't as locked down as it should be – that's the part of the phone's built-in firmware that stops you replacing the OnePlus OS with whatever else you want to install instead.