CSP (Content Security Policy) : iframe, image (img), video blocking

# CSP (Content Security Policy) : iframe, image (img), video blocking ``` document.referrer; // in javascript req.headers().get("Referer"); // in vert.x ```/ referrer 통해서 연결을 허용할 것인가? 말 것인가를 결정하는 거인듯? 그런데 CORS (Cross-Origin Resource Sharing) 하고는 좀 다른 개념인건가? 헷갈리네... ## RRA

1. MDN - CSP (Content Security Policy) policy directives
2. MDN - Cross-Origin Resource Sharing (CORS)
3. MDN - The X-Frame-Options response header