[whatwg] element "img" with HTTP POST method

[Adam Barth]

On Thu, Dec 9, 2010 at 4:46 PM, Tab Atkins Jr. <jackalmage at gmail.com> wrote:
> On Thu, Dec 9, 2010 at 11:01 AM, Adam Barth <w3c at adambarth.com> wrote:
>> We've seen use cases for a similar feature for iframes and hyperlinks.
>>  For example:
>>
>> <a href="/logout" post-data>Logout</a>
>>
>> would be more semantically correct that just <a
>> href="/logout">Logout</a> because it would generate a POST instead of
>> a GET.
>
> Why wouldn't <form method=post
> action=/logout><button>Logout</button></form> work, with some CSS to
> make it look like a link if you wanted that?

It's too much work.  :)

> On Thu, Dec 9, 2010 at 11:41 AM, Philipp Serafin <phil127 at gmail.com> wrote:
>> There are quite a number of older web forums that sanitize their HTML using black lists and would not strip new attributes like "post-data". For malicious users, it would be very easy to include e.g. <img src="./do_post.php" post-data="thread_id=42&post_content=Go visit (some spam URL)"> in their signature and have users doing involuntary posts by simply viewing a thread.
>
> Indeed.  You shouldn't be able to trigger POSTs from involuntary
> actions.  They should always require some sort of user input, because
> there is simply *far* too much naive code out there that is vulnerable
> to CSRF.

Unfortunately, the attacker can already trigger POSTs with involuntary
actions.  That code is already vulnerable attack, sadly.

Adam