com.apple.WebKit.Plugin.64??
iPhone 6s, iOS 9.1
It sounds like the plug-in wants to use information stored in your keychain for something acrobat. You can turn off the plug-in. See this Support Topic for details.
How to use Internet plug-ins in Safari for Mac - Apple Support
Thanks, MacJack!
You're welcome.
com.apple.WebKit.Plugin.64??