Signing onto Shoprite Wifi causes Google to lock my account Shoprite is a chain of grocery stores in the Northeast. They now have a special iOS app where you can scan your own groceries as you shop. When you leave, you simply pay for what was already scanned and skip the checkout line.
In order to use the app, you must be logged into the Shoprite WiFi network. However, every time I do that, I get an immediate notification from Google that says

Google Account xxxxxx Suspicious login detected. See google.com/blocked

The link goes to a webpage that says:

We blocked an application from signing in to your account
We recently denied a sign-in attempt from an application (like an email or chat client) or a mobile device because we weren’t sure it was really you. To prevent unauthorized access to your account, Google notifies you via email and/or SMS when we notice this type of suspicious sign-in attempt.

After that, my Gmail account is locked, and I have to request a text message to unlock it.
This is really strange since my Shoprite account doesn't have anything to do with my Google account. I have seen absolutely nothing on the Internet about this, and neither Google or Shoprite seem able to tell me exactly what is going on.
I have no idea why this is happening, and I thought maybe someone here can explain it to me. There are two explanations I can think of:

Shoprite is attempting to access my Google account. They're a pretty big public company, and I can't imagine them surreptitiously doing something like this.
My iPhone is attempting to access my Gmail while on Shoprite's WiFi, but why would that matter to Google? I've connected to other WiFi networks around (Amtrak, Starbucks, Cablevision, etc.) and Google doesn't care about those. Besides, the app that's accessing my Gmail account would be my iPhone's Mail.app which has been setup to do just that.

Any ideas what is going on?
I have had similar issues with Google. I connect to Google services in the background from what Google sees as a "new location". So, when I sign in from what it deems as an unusual location, I see these entries in my Recent Activity :



When I verify that it was me "by clicking the "Yes, that was me!" button, the next time I connect, I no longer get the security notifications. This seems to remediate the issue, but it doesn't explain to me why I'm getting the notifications in the first place. (I haven't been able to track down an explanation, only a way to get rid of the notifications.)