The default configuration of Microsoft Windows uses the Web Proxy Autodiscovery Protocol (WPAD) without static WPAD entries, which might allow remote attackers to intercept web traffic by registering a proxy server using WINS or DNS, then responding to WPAD requests, as demonstrated using Internet Explorer.  NOTE: it could be argued that if an attacker already has control over WINS/DNS, then web traffic could already be intercepted by modifying WINS or DNS records, so this would not cross privilege boundaries and would not be a vulnerability.  It has also been reported that DHCP is an alternate attack vector.