Microsoft Learned of IE Zero-Day Flaw Last September

Microsoft was aware months ago of a critical security vulnerability well before hackers exploited it to breach Google, Adobe and other large U.S. companies but did not patch the hole completely until Thursday.

The software giant had intended to release a patch for the flaw in February — more than four months after learning about it, but had to speed up that plan and role it out this week in the wake of news that Google and others had been hacked through the flaw, the world’s largest software maker acknowledged Thursday.

Meron Sellen, a security researcher at BugSec, an Israeli firm, quietly reported the vulnerability to Microsoft in September, according to security firm Kaspersky. Microsoft confirmed it learned of the so-called “zero-day” flaw months ago.