CVE-2019-18886: Prevent user enumeration using switch user functionality

Affected versions Symfony 4.2.0 to 4.2.11 and 4.3.0 to 4.3.7 versions of the Symfony Security/Http component are affected by this security issue. The issue has been fixed in Symfony 4.2.12 and 4.3.8. Note that no fixes are provided for Symfony 4.1 as they are not maintained anymore. Description T...