By default, WordPress only allows uploading certain file types. However, some files that are commonly used in everyday workflows are not fully permitted due to certain security concerns.
If you still want to use these files, they must be explicitly added to the allowed file types via a filter.
add_filter( 'upload_mimes', static function($mimes) {
$mimes['svg'] = 'image/svg+xml';
return $mimes;
});