Multiple vulnerabilities have been found in the Symfony PHP framework which could lead to open redirects, cross-site request forgery, information disclosure, session fixation or denial of service.
For the stable distribution (stretch), these problems have been fixed in version 2.8.7+dfsg-1.3+deb9u1.
We recommend that you upgrade your symfony packages.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/