Symfony 6.3.9 has just been released.
Here is the list of the most important changes since 6.3.8:

• bug #52786 [Serializer] Revert allowed attributes fix (@mtarld)
• bug #52780 [DependencyInjection] don't check parameter values if they are not set (@xabbuh)
• bug #52762 [VarExporter] Work around php/php-src#12695 for lazy objects, fixing nullsafe-related behavior (@nicolas-grekas)
• bug #52759 [VarExporter] Fix serializing objects that implement __sleep() and that are made lazy (@nicolas-grekas)
• bug #52767 [Serializer] Fix normalization relying on allowed attributes only (@mtarld)
• bug #52727 [String] Fix Inflector for 'icon' (@podhy)
• bug #52677 [Translation] [Lokalise] Fix language format on Lokalise Provider (@welcoMattic)
• bug #52715 [Cache] fix detecting the database server version (@xabbuh)
• bug #52688 [Cache] Add url decoding of password in RedisTrait DSN (@alexandre-daubois)
• bug #52172 [Serializer] Fix denormalizing empty string into object|null parameter (@Jeroeny)
• bug #52693 [Messenger] Fix message handlers with multiple from_transports (@valtzu)
• bug #52684 [PropertyInfo] Fixed promoted property type detection for PhpStanExtractor (@LastDragon-ru)
• bug #52681 [Serializer] Fix support for DiscriminatorMap in PropertyNormalizer (@mtarld)
• bug #52680 [Serializer] Fix access to private properties/getters when using the @Ignore annotation (@mtarld)
• bug #52713 [Serializer] Fix deserialization_path missing using contructor (@mtarld)
• bug #52683 [Serializer] Fix constructor deserialization path (@mtarld)
• bug #52707 [HttpKernel] Fix logging deprecations to the "php" channel when channel "deprecation" is not defined (@nicolas-grekas)
• bug #52589 [Serializer] Fix XML attributes not added on empty node (@mtarld)
• bug #52686 [Cache] fix detecting the server version with Doctrine DBAL 4 (@xabbuh)
• bug #52629 [Messenger] Fix support for Redis Sentinel using php-redis 6.0.0 (@pepeh)
• bug #52459 [Cache][HttpFoundation][Lock] Fix PDO store not creating table + add tests (@HypeMC)
• bug #52626 [Serializer] Fix denormalizing date intervals having both weeks and days (@oneNevan)
• bug #52578 [Serializer] Fix denormalize constructor arguments (@mtarld)
• bug #52526 Add some more non-countable English nouns (@paullallier)
• bug #52631 [DomCrawler] Revert "bug #52579 UriResolver support path with colons" (@lyrixx)
• bug #52618 [VarExporter] Fix handling mangled property names returned by __sleep() (@nicolas-grekas)
• bug #52588 [Messenger] Use extension_loaded call to check if pcntl extension is loaded, as SIGTERM might be set be swoole (Sergii Dolgushev)
• bug #52579 [DomCrawler] UriResolver support path with colons (@vdauchy)
• bug #52581 [Messenger] attach all required parameters to query (@xabbuh)

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