(Reuters) – Facebook Inc said on Friday it has discovered a bug that may have affected up to 6.8 million people who used Facebook login to grant permission to third-party apps to access photos.

The company said in a blog that the problem has been fixed but that it may have affected up to 1,500 apps built by 876 developers.

Facebook said some third-party apps may have gained access to a broader set of photos than usual for 12 days between Sept. 13 to Sept. 25.

The bug is the latest in a string of privacy problems the tech giant disclosed this year, including the massive Cambridge Analytica data scandal in April and a data breach of nearly 30 million accounts in October.

Facebook shares were down 1.3 percent at $143.07 in early trading on Friday. The Nasdaq composite index <.IXIC> fell 0.9 percent.

(Reporting by Angela Moon in New York Arjun Panchadar in Bengaluru; Editing by Arun Koyyur and Bill Trott)