Facebook has uncovered a bug that gave third party apps access to the photos of up to seven million users.

The company has apologised for the breach and said the issue has now been fixed.

It said the glitch was active for 12 days between the 13th and 25th of September.

The bug affected people who used Facebook to login to third party apps and granted permission to access their photos.

"When someone gives permission for an app to access their photos on Facebook, we usually only grant the app access to photos people share on their timeline," the company said in a message to developers.

"In this case, the bug potentially gave developers access to other photos, such as those shared on Marketplace or Facebook Stories.

"The bug also impacted photos that people uploaded to Facebook but chose not to post."

The social media giant believes the glitch may have affected up to "eight million users and up to 1,500 apps built by 876 developers."

It said users who may have been affected will be notified via a Facebook alert in the coming days.

The company is urging people to log in to any apps they have shared their Facebook photos with to check which photos they have provided access to.