Javascript is a high level, dynamically typed interpreted, sixth most popular programming language. It interacts with the user DOM to perform various functionalities. 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. There have been cases of Javascript security breaches all over ever since its release. Even Facebook hasn’t been all of from its vulnerabilities. Mark Zuckerberg’s own Facebook account was hacked and he was informed in prior of the security risk Facebook had. To do away with those security vulnerabilities, experts suggest some measures that should be implemented so as to contain the risk. Javascript experts feel that these vulnerabilities are a result of Javascript developers failing to incorporate these measures to contain those risks. 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. This is one of the most common vulnerability in an app. XSS occurs when any malicious or unwanted or unauthorised Javascript code snippet is run in the victim’s browser or in side the application. This can lead to the data being stolen, or the user being redirected, or compromising of the clipboard data, or browser’s history. This can not be filtered through a web app firewall as well. XSS occurs when the application uses data parameters and pass it to the browser without properly validating the data. Cross-Site Scripting (XSS) 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. Prevention 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. Cross-Site Request Forgery (CSRF) 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. Prevention Hackers normally use leaks/flaws in the authentication mechanism to impersonate other users. Session Management 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. Prevention Use strict mode whenever possible. This eliminates silent errors and shows them all the times. It helps the Javascript engine perform optimisations on the code. Strict Mode for Javascript 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. Sensitive Data Exposure Use strong algorithms for hashing passwords. Enforce stronger passwords. Use 2 factor authentication. Use Google authenticator. Password Management Secure: only to be used over HTTPS. Do not allow the cookie to be accessed via Javascript. Handling Cookies For cookies set the following flags: Only to be accessed by certain domains. Only accessible on certain paths. Expires after a stipulated time. Enforce proper cookie scoping. This article contains some parts that were taken from a talk titled “How To Write Secure JavaScript Applications” by Jared Smith at an event “Nodevember 2016”
