<ul><li>Fixed typo <code>return fasle</code> → <code>return false</code> in DomainNamesController::validateUrl() (MEDIUM)</li><li>Fixed broken HTML attribute <code>name="isDefautruealue="false"</code> → <code>name="isDefault" value="false"</code> in user_modal.php (MEDIUM)</li><li>Fixed missing event parameter in <code>#check_domain_form</code> submit handler — <code>function()</code> → <code>function(event)</code> in custom_js.php causing <code>event.preventDefault()</code> to throw ReferenceError (HIGH)</li><li>Fixed broken include path for countries.php in domains_list.php — corrected from <code>'../../../../administration/'</code> to <code>'/../../../administration/'</code> resolving to correct platform/administration path (HIGH)</li><li>Fixed missing slash separator in domain_form.php include — <code>$_SERVER['DOCUMENT_ROOT'].'platform/...'</code> → <code>rtrim($_SERVER['DOCUMENT_ROOT'],'/').'/'.'platform/...'</code> (MEDIUM)</li><li>Fixed unguarded <code>$_GET['domainid']</code> access without isset() in domain_form.php and actions.php → replaced with <code>!empty()</code> check (MEDIUM)</li><li>Fixed all unguarded <code>$_POST</code> accesses in add_update.php — added null coalescing <code>?? ''</code> defaults throughout (HIGH)</li><li>Fixed missing <code>global $domainsite_params</code> declaration in <code>checkDomain()</code> function in add_update.php causing Undefined variable warning (HIGH)</li><li>Fixed <code>$_SESSION['INSTANCE']</code> undefined key in add_update.php — added <code>?? 0</code> fallback (MEDIUM)</li><li>Fixed <code>$strDomainId</code> undefined variable in domains.php and settings.php — added null coalescing default at top of each file (MEDIUM)</li><li>Fixed <code>$rsDomainType</code> undefined variable in settings.php — added null coalescing default (MEDIUM)</li></ul>