Slack: Bypass of the SSRF protection (Slack commands, Phabricator integration)

Abstract Some Slack features like "Integrations / Phabricator" and "Integration / Slash Commands" allow users to submit URL that will be accessed by the backend servers. A blacklist tries to forbid access to internal resources loopback, 10.0.0.0/8, 192.168.0.0/24, .... This blacklist can be...