ultimatemember/includes/lib/upload/um-image-upload.php

<?php
// Exit if accessed directly
if ( ! defined( 'ABSPATH' ) ) exit;

$dirname = dirname( __FILE__ );
do {
    $dirname = dirname( $dirname );
    $wp_config = "{$dirname}/wp-config.php";
    $wp_load = "{$dirname}/wp-load.php";
}
while( !file_exists( $wp_config ) );

if ( !file_exists( $wp_load ) ) {
    $dirs = glob( $dirname . '/*' , GLOB_ONLYDIR );


    foreach ( $dirs as $key => $value ) {
        $wp_load = "{$value}/wp-load.php";
        if ( file_exists( $wp_load ) ) {
            break;
        }
    }
}
require_once( $wp_load );

$ret['error'] = null;
$ret = array();

$id = $_POST['key'];
$timestamp = $_POST['timestamp'];
$nonce = $_POST['_wpnonce'];

UM()->fields()->set_id = $_POST['set_id'];
UM()->fields()->set_mode = $_POST['set_mode'];

/**
 * UM hook
 *
 * @type filter
 * @title um_image_upload_nonce
 * @description Change Image Upload nonce
 * @input_vars
 * [{"var":"$nonce","type":"bool","desc":"Nonce"}]
 * @change_log
 * ["Since: 2.0"]
 * @usage
 * <?php add_filter( 'um_image_upload_nonce', 'function_name', 10, 1 ); ?>
 * @example
 * <?php
 * add_filter( 'um_image_upload_nonce', 'my_image_upload_nonce', 10, 1 );
 * function my_image_upload_nonce( $nonce ) {
 *     // your code here
 *     return $nonce;
 * }
 * ?>
 */
$um_image_upload_nonce = apply_filters( "um_image_upload_nonce", true );

if(  $um_image_upload_nonce ){
	if ( ! wp_verify_nonce( $nonce, 'um_upload_nonce-'.$timestamp ) && is_user_logged_in() ) {
	    // This nonce is not valid.
	    $ret['error'] = 'Invalid nonce';
	    die( json_encode( $ret ) );
	}
}

if(isset($_FILES[$id]['name'])) {

    if(!is_array($_FILES[$id]['name'])) {
	
		$temp = $_FILES[$id]["tmp_name"];
		$file = $id."-".$_FILES[$id]["name"];
		$file = sanitize_file_name($file);
		 $ext = strtolower( pathinfo($file, PATHINFO_EXTENSION) );

		$error = UM()->files()->check_image_upload( $temp, $id );
		if ( $error ){
			
			$ret['error'] = $error;
		
		} else {
			$file = "stream_photo_".md5($file)."_".uniqid().".".$ext;
			$ret[ ] = UM()->files()->new_image_upload_temp( $temp, $file, UM()->options()->get('image_compression') );
			
		}

    }
	
} else {
	$ret['error'] = __('A theme or plugin compatibility issue','ultimate-member');
}
echo json_encode($ret);