XSS Prevention begins at understanding the vulnerability through examples.
Cross-Site Scripting is one of the most common web application vulnerabilities posing threat to around 65% of all websites globally. A typical attack involves delivering malicious content to users in a bid to steal data or credentials.
While it’s comparatively easier to patch this kind of vulnerability with certain data validation logic and encoding outputs, most website owners do not even know about XSS vulnerability and how it could be harming their end users.
According to the Open Web Application Security Project
Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious scripts are injected into otherwise benign and trusted websites. XSS attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user. Flaws that allow these attacks to succeed are quite widespread and occur anywhere a web application uses input from a user within the output it generates without validating or encoding it.
In other words, such vulnerability allows a web application to echo malicious inputs that are executed back into the user’s browser. A successful attack leads to stealing information, session hijacking, malware, sensitive information leakage, and display of malicious advertisements.
There are many ways in which attackers can spot, plant, and exploit a vulnerability within the web applications. Here are a few of the most common techniques or types.
Reflective XSS attacks have increased multiple times in recent years with URL shortening services that make fake URLs look benign.
Before you can start taking steps to stop Cross-Site Scripting attacks on the website, it is critical to understand the problem. What is it that the hackers exploit? What are the common weaknesses that often lead to XSS attacks? Here are some of the examples that will help developers and security experts.
No business can afford to lose the trust of its users by executing commands that actually risk their information. That is exactly why detection, prevention, and remediation are always a pressing issue with vulnerabilities like XSS. Although many companies think of it as a smaller issue, the implications can be huge. The data breach, financial losses, and loss of customer trust are only some of the damages XSS can cause.
A lot of organizations presume that cross-site scripting isn’t exactly a pressing issue. It doesn’t actually put server or database in grave danger after all. However, they should understand that if users are compromised, sooner or later, the problems will challenge your website security.
Web application developers should fundamentally analyze code for smarter interpretation. The user inputs should be filtered from the malicious chain of commands. Malicious codes are widely injected in GET or POST parameter. Both reflective and persistent cross-site scripting vulnerabilities can be dealt with validation.
However, validation brings several code changes leading to last-minute whitelisting and blacklisting, which often leads to rejection of real users. In-depth, the on-going analysis is required for precision.
Why should browser execute inputs as code and not just simple data? Along with validation, filtration and escaping are the best practices to avoid XSS. All the inputs including special characters should be ciphered in respective HTML or URL codes. Other than that, you can also look into inbound/outbound handling too.
A positive XSS prevention model is incomplete with thorough testing of the input fields at regular intervals. Web application scanning has been the ultimate took for raising red flags efficiently for many years now. However, today there is a need for manual expert intervention to test web applications for logics that a machine can’t.
Manual application assessment through web application scanning can reveal vulnerabilities in detail. Moving forward, if an organization doesn’t have time, resources, or patience to mend found vulnerabilities, a web application firewall can prevent your application from executing malicious inputs, securing you and your users.
Founder & Chief Marketing Officer, Indusface
Venky has played multiple roles within Indusface for the past 6 years. Prior to this, as the CTO @indusface, Venky built the product/service offering and technology team from scratch and grew it from ideation to getting initial customers with a proven/validated business model poised for scale. Before joining Indusface, Venky had 10+ years of experience in the security industry and had held various mgmt/leadership roles in Product Development, Professional Services, and Sales @Entrust.