Заголовок Header set X-XSS-Protection "1; mode=block" стал небезопасным

Если у Вас именно такой заговок установлен, то в настоящее время продвинутые сервисы проверки напишут:

"Your configuration requests blocking when XSS attacks are detected, which is potentially dangerous as it allows attackers to selectively disable portions of of JavaScript code. The only safe approach is to explicitly disable browser-based XSS protection."

Ибо:

"Some browsers ship with so-called XSS Auditors, built-in defenses against XSS. Although these defenses work against simple reflective XSS attacks, they can be abused by skillful attackers to add weaknesses to otherwise secure web sites. These dangers are present in both filtering and blocking modes. At this time, the Safari browser ships with its XSS defenses enabled by default. For this reason, the best approach is to explicitly disable this functionality."

Тоесть теперь правильнее отключать эту защиту путём:

Header set X-XSS-Protection "0"

И тогда:  "Great. XSS protection is explicitly disabled, making this web site safe even with browsers that have this functionality enabled by default"

Весьма удивлён такими изменениями !