Tom's Hardware reports security researcher Charlie Miller discovered that all of Apple's MacBooks, including the Air and Pro lines, have a scary security flaw. Miller found that the MacBooks share a common password that's required to gain access to the battery's controller chip, which could enable hackers to make the battery useless, turn off the overheating failsafe or install malware that would persist even with full HDD wipes.
Miller found that MacBooks share a common password that's required to gain access to the controller chip that's responsible for the battery. A hacker could hijack the firmware to render a lithium-ion battery useless so it no longer holds a charge – or even worse, turn off the temperature management to make it potentially explode.
MacBook batteries, and nearly all other laptop batteries, usually have a failsafe feature in them to prevent overheating, but anything is possible as we've seen in past reports of battery explosions.
Another scary possibility is that the battery firmware could become home to malware that would persist even with full hardware wipes or replacements. Battery removal isn't a common way to troubleshoot malware.