Use Outlook? Hackers can take over your PC with a single email, you must update immediately

Worse still, the vulnerability that enables this attack is known to hackers worldwide. This is known as a "zero-day flaw" because there are zero days before the secret is out, meaning it's a race against time to update your device with the fix before cybercriminals attack you. Without the fix, mistakenly opening a malicious email is enough to let hackers wrest control of your device.

Until you're sure that you've updated to the latest iteration of the software, do not open attachments or files you weren’t expecting, even if the sender looks familiar. Microsoft has credited a researcher who used Anthropic's Artificial Intelligence (AI) tool Claude to find the flaw. Artificial Intelligence is playing a prominent role in cybersecurity circles.

These tools are increasingly being used to interrogate the code that our digital infrastructure is built upon, exposing weaknesses that human reviewers might miss. Microsoft promised to leverage Artificial Intelligence to sniff out new flaws inside its software earlier this year. Last month, ChatGPT was used to uncover a critical flaw in PHP, the language underpinning millions of websites that led to UK Government taking websites offline and Amazon raising the alarm about a dramatic uptick in attacks.

Google has switched to a fortnightly release for security updates to its Chrome web browser to combat the faster pace of discovery for these flaws. LATEST DEVELOPMENTS Amazon redesigns its Kindle lineup to be lighter, faster, and more colourful Monzo issues Black Friday warning to 15.2 million customers RIP Facebook Events? WhatsApp's new feature helps you RSVP to plans BBC to add AI assistant called 'Iggy' to iPlayer iPhone Duo review With the fix now available, you must update to the latest version of Microsoft 365 to resolve the vulnerability.

In Outlook, navigate to File > Account > Update Options > Update Now. If you're using classic Outlook to manage your emails, you'll need to use File > Office Account, then Update Options > Update Now if available. If you don't see the option, you're already up to date.

Microsoft rolled out the fix to Outlook alongside a slew of other flaws across its operating system and applications. The US firm releases bug fixes every month in what's known as Patch Tuesday. The latest release contained fixes for 1,094 flaws.

Alongside the "zero-day" vulnerability, 63 other bugs were rated as "critical". That's slightly down from the previous Patch Tuesday, which was released in mid-October and broke records for fixing over 1,400 flaws in the desktop operating system. Jack Bicer, Director of Vulnerability Research at Action1, said: "Microsoft's November 2026 Patch Tuesday delivers another exceptionally large update cycle, with 1,093 patches, including 63 critical vulnerabilities and 1 actively exploited zero-day.

While that is down from October's record-breaking 1,409 patches, it still marks the third consecutive month with patch volumes at levels that would have been extraordinary earlier this year." Mr Bicer added: "Email is the easiest door into any company, and this flaw turns one opened file into a stolen identity. A captured hash can let an attacker sign in as the victim, read their data, and move to other systems they can reach. "If the victim is an administrator or a finance user, the damage grows fast.

Because the warning users are trained to watch for never appears, even careful staff can be caught." The same AI tools that've helped Microsoft roll out a record number of patches — and thousands of vulnerabilities in its software — can be used by cybercriminals to launch more sophisticated attacks, faster than ever before. It's essentially an arms race, and staying current with patches has never been more important. That's why it's especially important to ensure your device is running Windows 11 — the latest operating system.

This ensures you'll be able to install every security patch released. If you missed the memo, the US tech firm pulled the plug on its immensely popular Windows 10 operating system late last year, marking the end of a decade of support. For those who haven't taken action to update their devices, you're leaving yourself vulnerable to an increased risk of malware, ransomware, cyberattacks, and worse.

That's because, without regular security updates and bug fixes from Microsoft, there's nothing to stop criminals from exploiting vulnerabilities unearthed within the operating system. However, Microsoft has quietly given Windows 10 users a welcome lifeline, stretching its Extended Security Update (ESU) programme by an extra year. The new deadline is now October 12, 2027, rather than the original October 2026 cutoff.