Strange Keychain Popups in Safari I just upgraded my Mac from El Capitan to Sierra, and now I'm getting some weird keychain popups in Safari.

When I browse Safari, if I visit a site for which I have credentials stored, a dialog pops up asking me whether or not to allow Safari to use the keychain info for an entirely different URL than the one I'm currently visiting (the url is a development server of mine). Here's a screenshot of it happening on Stack Overflow:



Translation by @owlswipe: Safari wants to access confidential information stored in [website] in your keychain with buttons for Always Allow, Allow, and Deny.

Then it gets weirder: when I click "allow", a second prompt appears, requesting an administrator's password and mentioning SteerMouse, a system settings extension for advanced mouse settings that I've installed.



Translation by @owlswipe: For security reasons, please enter an administrator's password to confirm the action. You can add "SteerMouse Manager" to the list of input helpers in System Preferences to stop displaying this password dialog. with a username and password field and buttons for Cancel and OK.

I don't have any reason to think that SteerMouse is trying to do anything nefarious here, as it's a widely recommended, popular product. But all this seems a little weird.

I know I can probably make it shut up by doing what the dialog says, but before I do so, can anyone explain what is going on here?
Open Keychain Access.app in your Applications > Utilities folder. 
Highlight the login keychain on the left sidebar.
Select one of the sites you see the popup from the list of credentials and double-click to get the info panel.
On that panel select "Access Control".
Below "Always allow access by these applications" click on +, and navigate to Safari in your Applications folder. Save changes.
Close Keychain Access and restart Safari.


(adapted from this answer. You may need to do steps 3-5 for each site for which that problem is occurring; I'm not certain.)