Microsoft says it has fixed a flaw in its Internet Explorer browser that left millions of users exposed to cyber attacks.
Redmond has said it will release an emergency patch to fix the security glitch on Friday, 21 September. It had previously announced a workaround that would temporarily protect users against threats.
The flaw was discovered by Luxembourg-based researcher Eric Romang, who said it affected all versions of the browser, except IE10, the most recent version. However, because IE10 is so new it is not being used by a large number of people.
If exploited by cyber attackers the flaw could result in users' PCs being taken over and malware being planted on them.
The incident prompted Germany's government to warn businesses not to use IE.
"This cumulative update for Internet Explorer has an aggregate severity rating of Critical," Microsoft said on its blog. "We recommend that you install this update as soon as it is available. If you have automatic updates enabled on your PC, you won't need to take any action, it will automatically be updated on your machine."
The blog also said other issues will be fixed along with this critical one.
According to Reuters, the company has also stressed that the "vast majority" of users were not attacked as a result of the flaw.
Internet Explorer has seen its market share steadily eroded over the last few years as rivals such as Google Chrome and Firefox enter the market.
Currently IE has around 33% of the world's browser market, just behind Chrome on 34%. However at its peak IE claimed around 70% of the market.