A new Windows zero-day allows threat actors to use malicious JavaScript files to bypass Mark-of-the-Web security warnings. Threat actors are already seen using the zero-day bug in ransomware attacks.

Attackers frequently send malicious JavaScript files through bogus emails. It's easy to block these files from reaching a hapless user. Here's how.

Unlike previous SVG-based threats that relied on hosted payloads or third-party file sharing, this campaign runs entirely within the client’s browser. By avoiding executable drops and leveraging ...