REDMOND, WASHINGTON - The National Security Agency has discovered a major security flaw in Microsoft's Windows operating system and tipped off the company so that it can fix it.

Microsoft made a software patch to fix it available Tuesday and credited the agency as the flaw's discoverer.

The company said it has not seen any evidence that hackers have used the technique discovered by the NSA.

"Customers who have already applied the update, or have automatic updates enabled, are already protected," said Jeff Jones, a senior director at Microsoft, in a statement.

Priscilla Moriuchi, who retired from the NSA in 2017 after running its East Asia and Pacific operations, said this is a good example of the ``constructive role'' that the NSA can play in improving global information security. Moriuchi, now an analyst at the U.S. cybersecurity firm Recorded Future, said it's likely a reflection of changes made in 2017 to how the U.S. determines whether to disclose a major vulnerability or exploit it for intelligence purposes.

The revamping of what's known as the "Vulnerability Equities Process'' put more emphasis on disclosing unpatched vulnerabilities whenever possible to protect core internet systems and the U.S. economy and general public.

Those changes happened after a group calling itself "Shadow Brokers'' released a trove of high-level hacking tools stolen from the NSA.