Google Chrome before 4.0.249.89, when a SOCKS 5 proxy server is configured, sends DNS queries directly, which allows remote DNS servers to obtain potentially sensitive information about the identity of a client user via request logging, as demonstrated by a proxy server that was configured for the purpose of anonymity.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A13926
http://www.vupen.com/english/advisories/2010/0361
http://www.securityfocus.com/bid/38177
http://sites.google.com/a/chromium.org/dev/Home/chromium-security/chromium-security-bugs
http://securitytracker.com/id?1023583
http://secunia.com/advisories/38545
http://googlechromereleases.blogspot.com/2010/02/stable-channel-update.html