Recently, very important security issues were discovered involving Siri, that seems to grant access to unauthorized users browsing through photos and contacts on locked iPhone's. The vulnerability was demonstrated in several videos, using Siri to access Twitter and search for emails or phone numbers. And with the help of 3D Touch anyone can open a Contacts and Photos, even if the device is locked.
Not long ago, people who updated their iPhone's to latest iOS 9.3 were unable to open links in Safari, Chrome, Mail and other apps, turning smartphones into regular mobile terminals.
After a week of waiting, Apple released iOS 9.3.1, a minor update that fix the problem exclusively with Safari and web links. At the same time, on certain iPhone's (6s and 6s Plus), iOS 9.3.1 opens the door to a pretty hefty vulnerability.
In the past, such a vulnerability would require another patch and update to be resolved, but it looks like Apple found a clever solution to fix it. Basically, the whole process has been carried out at server level meaning that doesn’t require any action on user’s part. Now, if the iPhone is locked and you want to perform a Twitter search via Siri, you'll get the answer “You’ll need to unlock your iPhone first”.
Another Siri error, quite favored by some users, was apparently adjusted by Apple, bug which let you activate Night Shift Mode while Low Power Mode is enabled. This is apparently no longer possible, Siri cautioning users that this is not possible and must disable Low Power Mode to use Night Shift.
The first iOS 9.3 beta versions, Night Shift worked on Low Power Mode, since beta 4, Apple changed things for unknown reasons.