The issue here is typically “ cross-site tracking,” which relies on passive linking among different sites. That appears to be due to poor security practices at some institutions, maybe owing to them licensing the same server software to handle their customers’ needs. You may find, however, that after updating Safari or macOS you can longer get features on a financial site to work. That may be nice for any site you visit, but it’s particularly critical for ones you use for banking, bill payment, and other financial purposes. When you see the lock icon to the left of a website’s URL in the Address and Search bar in Safari, you assume the site is secure.
