GHSA-xx3c-qf5g-hc39

### Description Symfony Mailer selects a transport via the `MAILER_DSN` environment variable / configuration (e.g. `smtp://...`, `sendmail://...`, `native://default`). `SendmailTransport` invokes the local `sendmail` binary and supports two modes: `-bs` (speak SMTP over stdin: the default) and `-t` (read the message on stdin, pass recipients as command-line arguments). In `-t` mode, recipient addresses are appended to the sendmail command line **without a `--` end-of-options separator**. A recipient address beginning with `-` (which `Symfony\Component\Mime\Address` accepts as valid) is therefore interpreted by sendmail as a command-line option rather than an address. ### Resolution The `SendmailTransport` transport now ensure `--` is set before the list of recipients. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/c45144862dc289d03952f41f6078174089a3afc6) for branch 5.4. ### Credits Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.