The tech giant revealed the worrying glitch as it launched its latest operating system – iOS 12.1.3 for the iPhone, iPad and HomePod.
While the update does not have any new features, it claims to have patched up major bugs affecting its products.
Among them are slight software glitches affecting Messages and the CarPlay function.
But the update also revealed a shocking lapse in the FaceTime video calling software – that could have allowed hackers to access it.
Apple’s Support website breaks down all the security updates included in iOS 12.1.3.
It reads: “A remote attacker may be able to initiate a FaceTime call using arbitrary code execution.”
The site goes on to state that this has been fixed by addressing a “buffer overflow issue.”
Apple said the FaceTime bug impacted the iPhone 5S and later, iPad Air and later, as well as the 6th generation iPod Touch.
The bug would have allowed attackers to execute malicious code – but it has since been fixed, according to Apple boffins.