EVOLUTION-MANAGER

Edit File: username.php

<?php
/**
 * @package    Joomla.Installation
 *
 * @copyright  Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later; see LICENSE.txt
 */

defined('JPATH_BASE') or die;

use Joomla\CMS\Filter\InputFilter;

/**
 * Form Rule class for the username.
 *
 * @since  3.9.4
 */
class InstallationFormRuleUsername extends JFormRule
{
	/**
	 * Method to test a username
	 *
	 * @param   SimpleXMLElement  $element  The SimpleXMLElement object representing the <field /> tag for the form field object.
	 * @param   mixed             $value    The form field value to validate.
	 * @param   string            $group    The field name group control value. This acts as an array container for the field.
	 *                                      For example if the field has name="foo" and the group value is set to "bar" then the
	 *                                      full field name would end up being "bar[foo]".
	 * @param   Registry          $input    An optional Registry object with the entire data set to validate against the entire form.
	 * @param   JForm             $form     The form object for which the field is being tested.
	 *
	 * @return  boolean  True if the value is valid, false otherwise.
	 */
	public function test(SimpleXMLElement $element, $value, $group = null, JRegistry $input = null, JForm $form = null)
	{
		$filterInput = InputFilter::getInstance();

if (preg_match('#[<>"\'%;()&\\\\]|\\.\\./#', $value) || strlen(utf8_decode($value)) < 2
			|| $filterInput->clean($value, 'TRIM') !== $value
			|| strlen(utf8_decode($value)) > $element['size'])
		{
			return false;
		}

return true;
	}
}