[MEDIUM] CVE-2020-5274: Fix Exception message escaping rendered by ErrorHandler

PKSA-879x-hms2-k3mp CVE-2020-5274 GHSA-m884-279h-32v2

Affected package: symfony/error-handler

Affected version: >=4.4.0,<4.4.4|>=5.0.0,<5.0.4

Reported by:
GitHub, FriendsOfPHP/security-advisories