Apple released a software update on Wednesday for iPhones and iPads fixing a bug that allowed law enforcement to extract messages that had been deleted or disappeared automatically from messaging apps. This was because notifications that displayed the messages’ content were also cached on the device for up to a month.

In a security notice on its website, Apple said that the bug meant “notifications marked for deletion could be unexpectedly retained on the device.”

This is a clear reference to an issue revealed by 404 Media earlier this month. The independent news outlet reported that the FBI had been able to extract deleted Signal messages from someone’s iPhone using forensic tools, due to the fact that the content of the messages had been displayed in a notification and then stored inside a phone’s database — even after the messages were deleted inside Signal.

After the news, Signal president Meredith Whittaker said the messaging app maker asked Apple to address the issue. “Notifications for deleted messages shouldn’t remain in any OS notification database,” Whittaker wrote in a post on Bluesky.

It’s unclear why the notifications’ content was logged to begin with, but today’s fix suggests it was a bug. 

Apple did not immediately respond to a request for comment, asking why the notifications were being retained. The company also backported the fix to iPhone and iPad owners running the older iOS 18 software.

Privacy activists expressed alarm when they learned that the FBI had found a way around a security feature that is used daily by at-risk users. Signal, like other messaging apps such as WhatsApp, allow users to set up a timer that instructs the app to automatically delete messages after a set amount of time. This feature can be helpful for anyone who wants to keep their conversations secret in the event that authorities seize their devices.