How Can I Safeguard Against Malicious Code in Cookies?

You should never trust anything sent from the user. Always assume the worst when it comes to data from clients.

Using a Web Application Firewall (WAF) can help check cookies from clients. Just remember, if you're not executing what’s in those cookies, you may be safer than you think.

HttpOnly cookies can't be accessed or modified by client-side scripts like JavaScript, so users can't directly change them. On the server side, you can't definitively tell if a cookie is HttpOnly just by looking at the request. It's all about how you set them; always validate and sanitize cookie data to prevent malicious input.

Once a cookie is treated as text on the server, you can do various checks to see if it's valid. Just ensure you validate it properly before taking any action.

The best way to keep cookies safe is to sign them and verify their contents using keys. Anything less is just asking for trouble.