Symfony 5.4.12 has just been released.
Here is the list of the most important changes since 5.4.11:

bug #47391 [LokaliseBridge] Fix push command –delete-missing options when there are no missing messages (@rwionczek)
bug #47368 [Security] Count remember me cookie parts before accessing the second (@MatTheCat)
bug #47358 Fix broken request stack state if throwable is thrown. (@Warxcell)
bug #47304 [Serializer] Fix caching context-aware encoders/decoders in ChainEncoder/ChainDecoder (@Guite)
bug #47329 Email image parts: regex for single closing quote (@rr-it)
bug #47283 [HttpFoundation] Prevent accepted rate limits with no remaining token to be preferred over denied ones (@MatTheCat)
bug #47128 [Serializer] Throw InvalidArgumentException if the data needed in the constructor doesn’t belong to a backedEnum (@allison guilhem)
bug #47273 [HttpFoundation] Do not send Set-Cookie header twice for deleted session cookie (@X-Coder264)
bug #47255 [Serializer] Fix get accessor regex in AnnotationLoader (@jsor)
bug #47238 [HttpKernel] Fix passing null to trim() method in LoggerDataCollector (@SVillette)
bug #47216 [Translation] Crowdin provider throw Exception when status is 50x (@alamirault)
bug #47209 Always attempt to listen for notifications (@goetas)
bug #47211 [Validator] validate nested constraints only if they are in the same group (@xabbuh)
bug #47218 [Console] fix dispatch signal event check for compatibility with the contract interface (@xabbuh)
bug #47200 [Form] ignore missing keys when mapping DateTime objects to uninitialized arrays (@xabbuh)
bug #47189 [Validator] Add additional hint when egulias/email-validator needs to be installed (@mpdude)
bug #47195 [FrameworkBundle] fix writes to static $kernel property (@xabbuh)
bug #47185 [String] Fix snake conversion (@simPod)
bug #47175 [DowCrawler] Fix locale-sensitivity of whitespace normalization (@nicolas-grekas)
bug #47171 [TwigBridge] suggest to install the Twig bundle when the required component is already installed (@xabbuh)
bug #47169 [Serializer] Fix throwing right exception in ArrayDenormalizer with invalid type (@norkunas)
bug #47161 [Mailer] Fix logic (@fabpot)
bug #47157 [Messenger] Fix Doctrine transport on MySQL (@nicolas-grekas)
bug #47155 [Filesystem] Remove needless mb_* calls (@HellFirePvP)
bug #46190 [Translation] Fix translator overlapse (@Xavier RENAUDIN)
bug #47142 [Mailer] Fix error message in case of an STMP error (@fabpot)
bug #45333 [Console] Fix ConsoleEvents::SIGNAL subscriber dispatch (@GwendolenLynch)
bug #47145 [HttpClient] Fix shared connections not being freed on PHP < 8 (@nicolas-grekas)
bug #47143 [HttpClient] Fix memory leak when using StreamWrapper (@nicolas-grekas)
bug #47130 [HttpFoundation] Fix invalid ID not regenerated with native PHP file sessions (@BrokenSourceCode)
bug #47129 [FrameworkBundle] remove the ChatterInterface alias when the chatter service is removed (@xabbuh)

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backwards-compatibility very closely, this should be quite easy. Use
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to detect the code you will need to change in your project and
read our upgrade
documentation to learn more.

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