Facebook is potentially facing huge fines from Ireland’s data protection commissioner, who has announced a fresh investigation into the social media giant.

The move comes after Facebook admitted another privacy error, possibly affecting 7m people. The bug may have allowed up to 1,500 apps get access to private photos held by users on the social site.

Facebook is already facing an official probe from the Irish data watchdog for a previous privacy leak in September, which the company said may have affected 30m people.

Under tough new EU GDPR rules, a company can be fined up to 4pc of its annual turnover. In Facebook’s case, this could amount to around €1.5bn.

The Irish data authority now has at least two serious investigations underway into Facebook, with 14 more also being undertaken against other tech multinationals. Because so many big tech companies choose Ireland as their European or global headquarters, the Irish data authority is responsible for investigating when there is a problem.

“The Irish DPC has received a number of breach notifications from Facebook since the introduction of the GDPR on May 25, 2018,” said a spokesman for the Irish watchdog.

“With reference to these data breaches, including the breach in question, we have this week commenced a statutory inquiry examining Facebook’s compliance with the relevant provisions of the GDPR.”

In a blog-post today, Facebook revealed more about the data leak and the people possibly affected.

“Our internal team discovered a photo API bug that may have affected people who used Facebook Login and granted permission to third-party apps to access their photos,” wrote Facebook executive Tomer Bar.

“We have fixed the issue but, because of this bug, some third-party apps may have had access to a broader set of photos than usual for 12 days between September 13 to September 25, 2018.

“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. 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. For example, if someone uploads a photo to Facebook but doesn't finish posting it - maybe because they've lost reception or walked into a meeting - we store a copy of that photo so the person has it when they come back to the app to complete their post.”

“Currently, we believe this may have affected up to 6.8 million users and up to 1,500 apps built by 876 developers. The only apps affected by this bug were ones that Facebook approved to access the photos API and that individuals had authorized to access their photos.

“We're sorry this happened. Early next week we will be rolling out tools for app developers that will allow them to determine which people using their app might be impacted by this bug. We will be working with those developers to delete the photos from impacted users.

“We will also notify the people potentially impacted by this bug via an alert on Facebook. We are also recommending people log into any apps with which they have shared their Facebook photos to check which photos they have access to.”

Online Editors