I recommend taking frequent looks at your access log for the URLs you're serving up. One day you may discover you're part of something you don't want to be part of.<p>This doesn't enable anything that wasn't already possible; it would be trivial for a bad actor to put up a redirector like this, after all. Still, at least when they do that, it's something they did and you have no responsibility.<p>I don't even know exactly what it is you don't want to be part of. It's just the possible range of URLs you probably will eventually start seeing come through will cross some sort of line for almost any given individual.
Back in 2008 (high school) I discovered this exact method enabled automatic creation of google accounts from many different visitor ip addresses, because google signup form did not have csrf protection. It was possible to hide all (pre-filled) form values except the captcha from the user. So to the user it looked like they were just filling out a captcha on a random website, but actually they were creating a new google account (using their IP address).<p>I hadn't heard of responsible disclosure at the time. ¯\_(ツ)_/¯
Awesome! Thanks for sharing. This is going to be really useful for doing CSRF attacks in XSS challenges at CTFs. I always just write the javascript to construct and post the form by hand, but this will be much faster, especially because you can just iframe it.
There should be no forms on the internet that allow CSRF like this. I'd be more concerned about finding a form that allows this than any privacy issues around using this unknown service to submit forms.
Not saying the service owner is a bad guy but this is in the category of online tools that always makes me nervous, along with:<p>- password strength checkers<p>- JSON, YAML, EDN, whatever prettiers<p>- checksum generators<p>- Base64 (en|de)coders<p>- etc.
> If you're not comfortable with anyone seeing what you're sending,
> don't send it via a website you found out about 15 minutes ago.<p>Says it all.
For the use case described it seems like better UX to auto-fill a form via query params than to auto submit it for the user.<p>I mean that's essentially what it's doing — why bother using a third party service at all?