WP: Auto-update whitelisted set of plugins.

auto-update-plugins.php

<?php

add_filter( 'auto_update_plugin', 'wps_auto_update_specific_plugins', 10, 2 );
function wps_auto_update_specific_plugins ( $update, $item ) {
    // Array of plugin slugs to always auto-update
    $plugins = array (
        'akismet',
        'enhanced-media-library',
        'duplicate-page',
    );
    if ( in_array( $item, $plugins ) ) {
         // Always update plugins in this array
        return true;
    } else {
        // Else, use the normal API response to decide whether to update or not
        return $update;
    }
}