Sensitive data often walks a fine line, treading carefully between utility and vulnerability. It’s a veritable treasure trove for those with a legitimate use for it, while simultaneously serving as a beacon for nefarious threats and malicious exploits.

Among the numerous dangers lurking in the cyber landscape, cross-site scripting attacks or XSS attacks occupy a notable position due to their potential to compromise businesses significantly.

In this blog post, we delve into the specifics of what cross-site scripting attacks are, the different types that exist, and how businesses can implement robust countermeasures against these intrusions.

Cross Site Scripting Attacks Explained

Cross site scripting attacks are a breed of cyber-attack where an attacker injects malicious scripts into web pages viewed by unsuspecting users. These attacks manipulate the trust a user has in a seemingly safe web application.

The malicious code that the attacker injects is executed by the user’s web browser and can perform harmful actions, such as stealing sensitive information or assuming the identity of the user within the application, thereby wreaking havoc on both personal and corporate data.

The Triad of Cross Site Scripting Attacks: Stored, Reflected, and DOM-based

Understanding the landscape of cross-site scripting attacks involves familiarising oneself with their three main types: stored, reflected, and DOM-based.

1. Stored XSS Attacks: In a stored attack, also known as persistent or type-I XSS, the malicious script is directly embedded into a web page and stored on the server. Consequently, any user who navigates to the affected page unwittingly triggers the script execution. For instance, a malicious script injected into a comment section that is rendered to every visitor of the page can steal users’ sensitive data.

2. Reflected XSS Attacks: Unlike stored attacks, reflected or non-persistent attacks, do not permanently reside on a web page. Instead, the malicious script is part of the URL request made to the server, typically embedded into a web form field, like a search box. When an unsuspecting user submits the form or clicks on a maliciously crafted link, the embedded script is returned and executed by the user’s browser. Despite their temporary nature, reflected XSS attacks can be just as damaging, especially when coupled with phishing techniques.

3. DOM-based XSS Attacks: In DOM (Document Object Model) based XSS, the attack payload is executed as a result of modifying the DOM environment in the victim’s browser. Here, the HTML source page itself remains unchanged, making this type of attack stealthy and difficult to detect. The malicious script manipulates the web page’s structure, often altering how the page interacts with scripts, leading to unexpected and potentially harmful results.

Fortifying Your Business Against XSS Attacks

Cross site scripting attacks can be particularly insidious because they often masquerade as legitimate code, making detection a challenge. However, a well-rounded defence strategy can considerably mitigate these threats.

Stay Current with Software Updates

Firstly, maintaining the latest versions of your software is an essential line of defence. This includes your web browser, operating system, and any add-ons, plugins, or extensions that you employ.

Cyber attackers are quick to exploit security vulnerabilities present in outdated software. Regular updates from software providers often address these vulnerabilities, reducing potential attack vectors.

Leverage a Web Application Firewall

Another potent countermeasure against XSS attacks is the use of a web application firewall (WAF). A WAF acts as a protective shield between your web application and the internet, scrutinising HTTP requests to filter out malicious inputs. By blocking harmful scripts before they reach your web pages, a WAF adds an extra layer of security, providing more control over web traffic and ensuring a safer environment for your users.

In addition to providing standard protection, WAFs offer customisable security policies tailored to your specific needs. This adaptability means you can fine-tune your defences based on the nature and sensitivity of your web page or application.

Implement Content Security Policy

Lastly, implementing a Content Security Policy (CSP) can fortify your web applications against XSS attacks. CSP serves as a robust shield, preventing your web pages from executing inline scripts and mitigating the risk of XSS attacks.

CSP is essentially a whitelist specifying the domains that a browser should consider as valid sources of executable scripts. By controlling the resources allowed to load for a particular page, a CSP blocks malicious scripts, even if they manage to sneak into your web page. Thus, it’s one of the most powerful tools in your arsenal against XSS attacks.

While these preventive measures significantly fortify your defences, it’s important to remember that cybersecurity is an ongoing process. Regular audits, persistent monitoring, and staying abreast of the latest developments in cyber threats and security are key to maintaining a robust defence against XSS attacks.


Understanding cross-site scripting attacks and their various forms is the first step in protecting your business from potential harm. Armed with this knowledge, you can implement effective strategies such as keeping your software up to date, utilising a web application firewall, and employing a content security policy to fortify your defences against these potential threats.

However, maintaining vigilance and fostering a culture of cybersecurity within your organisation are ultimately the best defence against these and other cyber threats.