PowerDNS -- Insufficient validation in the HTTP remote backend

PowerDNS developers report:

An issue has been found in PowerDNS Authoritative Server when the HTTP remote backend is used in RESTful mode (without post=1 set), allowing a remote user to cause the HTTP backend to connect to an attacker-specified host instead of the configured one, via a crafted DNS query. This can be used to cause a denial of service by preventing the remote backend from getting a response, content spoofing if the attacker can time its own query so that subsequent queries will use an attacker-controlled HTTP server instead of the configured one, and possibly information disclosure if the Authoritative Server has access to internal servers.