Software called EngineerMode means hackers could do whatever they want with a phone as long as they have it in hand.

Hackers who get hold of some OnePlus phones can obtain virtually unlimited access to files and software through use of a testing tool called EngineerMode that the company evidently left on the devices. Robert Baptiste, a freelance security researcher who goes by the name Elliot Alderson on Twitter after the "Mr. Robot" TV show character, found the tool on a OnePlus phone and tweeted his findings Monday. Researchers at security firm SecureNow helped figure out the tool's password, a step that means hackers can get unrestricted privileges on the phone as long as they have the device in their possession.

The EngineeerMode software functions as a backdoor, granting access to someone other than an authorized user. Escalating those privileges to full do-anything "root" access required a few lines of code, Baptiste said.

The EngineeerMode software functions as a backdoor, granting access to someone other than an authorized user. Escalating those privileges to full do-anything "root" access required a few lines of code, Baptiste said.