Why use a whitelist for HTML sanitizing?

Posted by Carson Myers on Stack Overflow See other posts from Stack Overflow or by Carson Myers
Published on 2010-03-19T08:09:51Z Indexed on 2010/03/19 8:21 UTC
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html

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whitelist

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xss

I've often wondered -- why use a whitelist as opposed to a blacklist when sanitizing HTML input?

How many sneaky HTML tricks are there to open XSS vulnerabilities? Obviously script tags and frames are not allowed, and a whitelist would be used on the fields in HTML elements, but why disallow most of everything?

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