A malfunction in Facebook’s Software Development Kit that lets apps add Login With Facebook, sharing, and other features caused apps that integrate it like Timehop to repeatedly crash for about three hours. TechCrunch received a tip that developers were getting tons of user complaints and crash reports starting around noon pacific today due to a problem with the Facebook for iOS SDK. TechCrunch’s testing verified that products like Timehop, Joytunes’ Simply Piano, Momento GIFs, and more kept breaking when users access Facebook features or in some cases just opened the app.

This is a big issue for Facebook because it relies on these apps to drive user lock-in. If people use Facebook to log into or share from other apps, they’re less likely to delete their account. But if the Facebook developer platform screws up like this morning, developers could instead highlight sharing via Twitter or SMS, and divert ad buys to other platforms. Most problematically, the bug could push developers to other login platforms like Google’s or Apple’s new Sign In With Apple.

[Update: 3:45pm PT: Facebook has fixed the bug and apps integrated with the SDK are starting to work normally again. A Facebook spokesperson tells me “We started to work on the issue as soon as it was reported to us, and it has been resolved.” Facebook engineer Ram Sharma posted that “Our engineering team worked to resolve this issue as soon as it was discovered. It is now mitigated and app function should be restored.” Developers confirm the bug has been fixed. The rest of this article remains as originally published.]

The bug was initially submitted to Facebook’s developer forums by Ryan Layne. These crashes thwart normal usage of other apps, costing their developers ad views and in-app purchases, or leading their users to uninstall or abandon them.

The situation highlights the increasing centralization of the web as more and more companies depend on a small number of mobile, hosting, and social platforms. Earlier this month, a Google Cloud outage knocked down Snapchat and Discord. While these tools make it simpler to start a company or launch an app without having to build everything in-house, they introduce platform risk. Beyond technical outages, there’s also the concern that a platform could use its insights to copy its clients, or block them if they compete with the gatekeeper too vigorously as Facebook has done to chat and social media apps in the past.