[MEDIUM] SS-2018-008: BackURL validation bypass with malformed URLs

PKSA-r6q9-f6rj-1d2w GHSA-j982-5jv7-v43r

Affected package: silverstripe/framework

Affected version: >=4.0.0,<4.0.4|>=4.1.0,<4.1.1

Reported by:
GitHub, FriendsOfPHP/security-advisories