A security patch released by Microsoft earlier this month failed to fully fix a critical flaw in the U.S. tech company's SharePoint server software that had been identified at a hacking competition in May,

The U.S. Cybersecurity and Infrastructure Security Agency (CISA), in an alert, said it's aware of active exploitation of CVE-2025-53770, which enables unauthenticated access to SharePoint systems and arbitrary code execution over the network.

Dubbed a “zero-day” because it leverages a previously undisclosed digital weakness, the hacks allow spies to penetrate vulnerable servers and potentially drop a backdoor to secure continuous access to victim organisations.

The term "zero-day" attack refers to when a previously unknown vulnerability is targeted. Tens of thousands of servers are said to be at risk. While the issue is serious, it differs from several previous vulnerabilities related to Microsoft. The attack only affects on-premises servers; cloud-based servers are unaffected.

A major zero-day security vulnerability in Microsoft's widely used SharePoint server software has been exploited by hackers, causing chaos within businesses and government agencies, multiple outlets have reported. Microsoft announced that it had released a ...

It issued an alert about “active attacks” targeting its server software and urged customers to install new security updates that have been released.