Facebook Login - iOS 9 - Without Safari

Using 20150708 solved it for me in iOS 9.

Link to SDK: https://developers.facebook.com/resources/FacebookSDKs-iOS-20150708.pkg

Safari web view opening when logging to FB through iOS 9

From a product manager at Facebook in the "Facebook Developer Community" group.

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And my Reply, still waiting for a response:

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So it sounds like with SDK 4.6 they are forcing every login to use the Safari View Controller.

EDIT ----

And their response:
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Facebook Login SDK in IOS 9

This is by design and is using SFSafariViewController on iOS 9. As noted in the v4.6 changelog,

The SDK supports various iOS 9 features including Bitcode. In
addition, the SDK dialogs such as Login, Like, Share Dialogs
automatically determine the best UI based on the device, including
SFSafariViewController instead of Safari

We know this may be confusing at first but we definitely have the same goal as our developers to make sure the users get the best experience on iOS 9 and have a good Login experience. On iOS 8, the login will still prefer an app switch to the Facebook app.

Facebook Login - iOS 9 - Without Safari