https://www.techdirt.com/articles/20200114/10535843732/nsa-surprises-microsoft-with-vulnerability-disclosure-just-time-patch-tuesday.shtml

Given the NSA's track record with vulnerability disclosures, it's somewhat of an anomaly when it actually decides the security of millions of innocent computer users is more important than its exploitation of a security flaw. Ellen Nakishima has the details for the Washington Post:

The National Security Agency recently discovered a major flaw in Microsoft’s Windows operating system — one that could potentially expose computer users to significant breaches or surveillance — and alerted the firm of the problem rather than turn it into a hacking weapon, according to people familiar with the matter.