Symfony 6.0.0-RC1 has just been released. Here is a list of the most
important changes:

security #cve-2021-41268 [SecurityBundle] Default signature_properties to the previous behavior (@wouterj)
security #cve-2021-41267 [HttpKernel] Fix missing extra trusted header in sub-request (@jderusse)
security #cve-2021-41270 [Serializer] Use single quote to escape formulas (@jderusse)
bug #44230 [Console] Add Suggestion class for more advanced completion suggestion (@wouterj)
bug #44232 [Cache] fix connecting to local Redis sockets (@nicolas-grekas)
bug #44204 [HttpClient] fix closing curl multi handle when destructing client (@nicolas-grekas)
bug #44208 [Process] exclude argv/argc from possible default env vars (@nicolas-grekas)
bug #44188 [VarExporter] fix exporting declared but unset properties when __sleep() is implemented (@nicolas-grekas)
bug #44176 [Console] Default ansi option to null (@jderusse)
bug #44179 [WebProfilerBundle] Fix JS error when toolbar is reloaded (@jderusse)
bug #44177 [SecurityBundle] Remove Guard (@derrabus)
bug #44172 [Security] Guard is incompatible with Symfony 6 (@derrabus)
bug #44119 [HttpClient][Mime] Add correct IDN flags for IDNA2008 compliance (@j-bernard)
bug #44139 [WebProfilerBundle] Prevent installation of incompatible mailer component versions (@Anne-Julia Seitz)
bug #43917 Allow autodetecting mapping type for any object (@franmomu)
bug #44130 [SecurityBundle] Remove outdated conditions based on authenticatorManagerEnabled (@chalasr)
bug #44131 [Yaml] properly parse quoted strings tagged with !!str (@xabbuh)
bug #42323 [TwigBridge] do not merge label classes into expanded choice labels (@xabbuh)

Want to upgrade to this new release? Because Symfony protects
backwards-compatibility very closely, this should be quite easy. Use
SymfonyInsight upgrade reports
to detect the code you will need to change in your project and
read our upgrade
documentation to learn more.

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