WASHINGTON/SAN FRANCISCO: Apple is said to have left more than half a billion iPhones exposed to hackers.

The bug, which also exists on iPads, was discovered by ZecOps, a mobile security forensics company, while it was investigating a sophisticated cyberattack against its client.

Zuk Avraham, ZecOps’ CEO, said he found evidence the vulnerability was exploited in at least six cybersecurity break-ins.

An Apple spokesman acknowledged the vulnerability in Apple’s software for e-mail on iPhones and iPads, known as the Mail app. He said the company had developed a fix, which will be rolled out in a forthcoming update on millions of devices it has sold globally.