I suggested the same for Symfony's templates, see symfony/symfony#47715

…ThomasLandauer)

This PR was merged into the 6.2 branch.

Discussion
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[Security] Removing self-closing slash from `<input>`s

I suggested the same for Symfony's templates, see symfony/symfony#47715

Commits
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c08a0a8 Removing self-closing slash from `<input>`s

…#47715 (mpdude)

This PR was merged into the 6.4 branch.

Discussion
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[Form] Use self-closing `<input />` syntax again, reverting #47715

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix #53649
| License       | MIT

This PR reverts #47715 and puts the trailing slash back into `<input .../>` markup in the form themes.

The reasons are outlined in detail in #53649. Basically, the trailing slash in void elements like `<input>` is not required in HTML 5, yet it is perfectly valid and compliant with specs.

Writing markup that way is required to parse and process it with an XML parser, like `libxml2` underlying all of the PHP DOM, XML etc. extensions.

HTML 5 capable parser support has been added to PHP in php/php-src#12111 and will be available with PHP 8.4. So, we might want to remove the trailing slashes once Symfony requires at least PHP 8.4.

Commits
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8c92200 Revert #47715

* 6.4: (21 commits)
  [ErrorHandler] Add missing self-closing tags on link elements
  Fix merge (bis)
  Fix merge
  Add missing return type
  [FrameworkBundle] ConfigBuilderCacheWarmer should be non-optional
  [HttpClient] Fix pausing responses before they start when using curl
  [Notifier] Updated the NTFY notifier to run without a user parameter
  [Translation] Fix constant domain resolution in PhpAstExtractor
  separate child and parent context in NotificationEmail on writes
  [Mailer] [Mailgun] Fix sender header encoding
  do not overwrite the cache key when it is false
  [Mailer] [Scaleway] Fix attachment handling
  [Mailer] Throw TransportException when unable to read from socket
  [Serializer] Rewrite `AbstractObjectNormalizer::createChildContext()` to use the provided `cache_key` from original context when creating child contexts
  Revert #47715
  [HttpClient] Fix error chunk creation in passthru
  Adjusting and removing the 'review' attribute from the pt_br translation XML.
  [DependencyInjection] Fix loading all env vars from secrets when only a subset is needed
  Fix option filenameMaxLength to the File constraint (Image)
  [Serializer] Take unnamed variadic parameters into account when denormalizing
  ...

* 7.0: (21 commits)
  [ErrorHandler] Add missing self-closing tags on link elements
  Fix merge (bis)
  Fix merge
  Add missing return type
  [FrameworkBundle] ConfigBuilderCacheWarmer should be non-optional
  [HttpClient] Fix pausing responses before they start when using curl
  [Notifier] Updated the NTFY notifier to run without a user parameter
  [Translation] Fix constant domain resolution in PhpAstExtractor
  separate child and parent context in NotificationEmail on writes
  [Mailer] [Mailgun] Fix sender header encoding
  do not overwrite the cache key when it is false
  [Mailer] [Scaleway] Fix attachment handling
  [Mailer] Throw TransportException when unable to read from socket
  [Serializer] Rewrite `AbstractObjectNormalizer::createChildContext()` to use the provided `cache_key` from original context when creating child contexts
  Revert #47715
  [HttpClient] Fix error chunk creation in passthru
  Adjusting and removing the 'review' attribute from the pt_br translation XML.
  [DependencyInjection] Fix loading all env vars from secrets when only a subset is needed
  Fix option filenameMaxLength to the File constraint (Image)
  [Serializer] Take unnamed variadic parameters into account when denormalizing
  ...