Ever since its advent in 1995, it has evolved a lot, now its being used for cross platform development as well, with tools like PhoneGap and for server side development with NodeJS.
One important thing to note is that “anything where we can get input to our application and back to the backend is a potential hack factor or vulnerability factor”. These would include Query Parameters, URL path, PUT/POST parameter, Cookies, Referrer headers, file uploads, Emails, Form fields, Web sockets, browser’s local/session storage etc.
XSS occurs when the application uses data parameters and pass it to the browser without properly validating the data.
Validate and sanitise all the user based inputs. Encode the output for specific contents, especially in cases where the output contains HTML tags. Set proper headers like Strict transport security, X-frame-options, X-XSS-protection, X-Content-Type-Options, Content-Security-Policy.
Cross-Site Request Forgery (CSRF)
This is pronounced as “see-surf”. It allows victim’s browser to make a forged HTTP request. It forces the end user to execute unwarranted actions on a web application in which they are currently authenticated. So while the user thinks that he is just browsing his own dashboard, the malicious code snippet loads in the background. For instance, there can be a hidden frame of Facebook on a page and while the user is browsing the page and is logged in to his Facebook account in the browser, the code in the background can make him post content on his behalf.
So, this gives the hackers the permission to force the user’s browser to generate requests without him knowing it.
Include a random, unpredictable token in requests. Add tokens to requests that can mutate the state of the application. Incorporating captcha. Origin of the request must be verified.
Hackers normally use leaks/flaws in the authentication mechanism to impersonate other users.
Don’t expose session tokens in the URL. Session tokens should have a timeout. Recreate session tokens after every successful login. Use HTTPS feor sending tokens. Use appropriate permissions. Use some well known authenticating mechanism.
Sensitive Data Exposure
Use SSL/TLS(HTTPS). Encrypt all sensitive data at rest and in transit. Do not store unnecessary data. Disable cache on forms that store sensitive data.
Use strong algorithms for hashing passwords. Enforce stronger passwords. Use 2 factor authentication. Use Google authenticator.
Enforce proper cookie scoping. Only to be accessed by certain domains. Only accessible on certain paths. Expires after a stipulated time.