Google has warned Windows and Mac users to urgently update their Chrome web browser due to a security bug that could let hackers hijack your computer.

Scroll down for Chrome update instructions issued by government agency CERT NZ.

The tech giant was forced to make an announcement as hackers managed to find the bug before Google found it.

Justin Schuh, Chrome's security engineer chief, warned users to update Chrome "right this minute" on Twitter, declaring it a "#PSA [Public Service Announcement]".

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Google revealed in a blog post that the update should fix the issue, which it described as "high" in severity.

There has been no information released about what will happen if users don't update their software.

"Access to bug details and links may be kept restricted until a majority of users are updated with a fix," Google said in a blog post warning about the discovery.

"We will also retain restrictions if the bug exists in a third party library that other projects similarly depend on, but haven't yet fixed."

The bug was discovered by Clement Lecigne of Google's Threat Analysis Group on February 27, Google said.

Google said that it's a type of bug that corrupts how a web app accesses a computer's memory and can be used to install malicious software on a computer, causing it to crash or behave strangely.

The bug was located in Google's FileReader, an application that is included in major browsers that lets the internet app access the contents of a PC.

"We would also like to thank all security researchers that worked with us during the development cycle to prevent security bugs from ever reaching the stable channel," said Abdul Syed, a Google Chrome engineer.

HOW TO UPDATE CHROME

• Check which version of Google Chrome you are using by typing chrome://settings/help into your browser. Versions earlier than 72.0.3626.121 are at risk.

• If you are on a laptop or desktop computer, open Chrome and visit chrome://settings/help. If you are not up-to-date, visiting the page should automatically update your browser.

• If you are on a mobile device, like a mobile phone or tablet, open Chrome and visit chrome://version. If you are not up-to-date, visit your app store and download the update.

Other web browsers are not at risk.