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These are not bugs. Siri is meant to be helpful and you can disable it easily.
 
I didn't really read into it... but if it has anything to do with Siri. It's a feature. Can you imagine having to input your password while your driving and trying to use siri? Death wish.

Feel insecure about that? Turn it off from the lock screen.
 
It works for some apps and not others. Maybe it's intentional or maybe it's a FaceBook flaw. Either way, if you don't want your locked phone to do anything, turn off everything that's available from the lock screen.
 
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