GHSA-mfqj-cqv3-h7xw

Description

### Problem Users were able to upload files with arbitrary MIME types to forms using _FileUpload_ or _ImageUpload_ elements with _allowedMimeTypes_ configured - uploading PHP files was **not** possible. The restriction was not enforced server-side because the _MimeTypeValidator_ was registered during form building before concrete form definition properties were applied, resulting in the validator never being added to the processing pipeline. ### Solution Update to TYPO3 version 14.3.5 LTS that fixes the problem described. ### Credits Thanks to Sébastien Convers for reporting this issue, and to Josua Vogel and Oliver Hader for fixing it.