Shopify does this. If you ever go to purchase a product on a Shopify 'site, and enter eg your e-mail address, it'll save it even if you decide to cancel and close the tab. Sometimes you receive spam from companies along the lines of marketing or "we noticed you didn't complete your purchase" type crap. Shit is rly invasive.

They can only send the marketing emails if you have the "send me marketing emails" checkbox checked when you type in your email address. Dark pattern, yeah.

Simplelogin is a godsend for this cancer

Have you checked to see if it’s stored in localstorage