Why is my speakerphone turning on automatically when answering or starting a call?

[AC Question]

I did not change any settings that I know of. Started after most recent update. I cannot find a setting to turn it off. Sometimes the speaker is on, but the button is not lit up. I have to turn it on and then back off to get the speaker to turn off.

 

[B. Diddy]

Welcome to Android Central! Which phone? Was the most recent system update a major one that upgraded the Android version?