Steps to reproduce

1. Install Ibexa DXP v4.5.
2. Create a form with a file field and button.
3. Configure the file field to allow only pdf extension.
4. Save the form and navigate to the created content.
5. Attempt to upload a file with a PDF extension (must be in capital letters).

Expected result:

The form should submit and save the data without error.

Actual result:

An error message is displayed: 'ErrorExtension not allowed.'"