My hardest riddle to solve so far was a form that I couldn't send. Because the address I entered was supposed to be validated by Google Maps. Obviously, there was neither a hint that this was to happen, nor any asking for consent before sending a query of someone's address to Google.
As with every development, clear design and good error handling are important. If you happen to build websites, you might try their usability with NoScript or uMatrix turned on before the deployment. :)
On the other hand, it's remarkable how many external resources are usually loaded, even though they have no impact on the functionality of the website whatsoever.
I'm using those tools for quite some time now, but I'm still surprised about how much unnecessary stuff is added to websites regularly.
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