/**
 * Allow SVG uploads for administrator users.
 *
 * @param array $upload_mimes Allowed mime types.
 *
 * @return mixed
 */
add_filter(
'upload_mimes',
function ( $upload_mimes ) {
// By default, only administrator users are allowed to add SVGs.
// To enable more user types edit or comment the lines below but beware of
// the security risks if you allow any user to upload SVG files.
if ( ! current_user_can( 'administrator' ) ) {
return $upload_mimes;
}

$upload_mimes['svg']  = 'image/svg+xml';
$upload_mimes['svgz'] = 'image/svg+xml';

return $upload_mimes;
}
);

/**
 * Add SVG files mime check.
 *
 * @param array        $wp_check_filetype_and_ext Values for the extension, mime type, and corrected filename.
 * @param string       $file Full path to the file.
 * @param string       $filename The name of the file (may differ from $file due to $file being in a tmp directory).
 * @param string[]     $mimes Array of mime types keyed by their file extension regex.
 * @param string|false $real_mime The actual mime type or false if the type cannot be determined.
 */
add_filter(
'wp_check_filetype_and_ext',
function ( $wp_check_filetype_and_ext, $file, $filename, $mimes, $real_mime ) {

if ( ! $wp_check_filetype_and_ext['type'] ) {

$check_filetype  = wp_check_filetype( $filename, $mimes );
$ext             = $check_filetype['ext'];
$type            = $check_filetype['type'];
$proper_filename = $filename;

if ( $type && 0 === strpos( $type, 'image/' ) && 'svg' !== $ext ) {
$ext  = false;
$type = false;
}

$wp_check_filetype_and_ext = compact( 'ext', 'type', 'proper_filename' );
}

return $wp_check_filetype_and_ext;

},
10,
5
);