[BUG] Image field does not check extension

[JarJak]

Description:

I have a field:

        image:
            label: Photo
            type: image
            extensions: [ gif, jpg, jpeg, png ]

But I am able to select any file (for example pdf file) from file browser to this field. Only the uploader excludes invalid file types.

Steps to reproduce:

1. Upload PDF file through another file field.
2. Try to set uploaded PDF as value of image field
3. Save

Expected result:

I would expect to not be able to select file other than types defined in field config
or an error on save.

Actual result:

Content saved without error, only the thumbnail displays an error.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Maybe this issue has been fixed in a recent release, or perhaps it is not affecting a lot of people?
It will be closed if no further activity occurs, because we like to keep the issue queue concise and actual.
If you think this issue is still relevant, please let us know. Especially if you’d like to help resolve the issue, either by helping us pinpointing the cause of a bug, or in implementing a fix or new feature.

[zomars]

Also I think the required attribute is not supported in an image field.