Apple tracks how iPhone owners use the "Stocks" and "Weather" widgets installed on each device, Uneasysilence claims. All mobile devices possess a unique International Mobile Equipment Identity number, and as the screenshot below indicates, the iPhone sends its user's unique IMEI to an Apple server each time the widgets perform a query. The data includes which stock ticker was queried.

This shouldn't surprise iPhone owners, because of course they all read Apple's terms of service before agreeing to it:

When you interact with Apple, we may collect personal information relevant to the situation, such as your name, mailing address, phone number, email address, and contact preferences; your credit card information and information about the Apple products you own, such as their serial numbers and date of purchase; and information relating to a support or service issue.

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