Gravatars Can Leak Users' Email Addresses
abell writes "Gravatar offers a global avatar service, using an MD5 hash of the user's email as avatar ID. This piece of information in some cases is enough to retrieve the original email address. Testing a simple attack on stackoverflow.com, I was able to determine the email addresses of more than 10% of the site's users."
Really? Are you familiar with MD5 collisions?
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