Security Tip: What Is XSS (Cross-Site Scripting) and How to Stop It

Cross-Site Scripting (XSS) is one of the most common website vulnerabilities, and it's also one of the easiest for attackers to exploit.

Here's how it works: your site takes input from a visitor — a search box, a comment form, a contact field — and displays it back on a page without properly escaping it. An attacker slips in a snippet of JavaScript, and when another visitor loads that page, the script runs in their browser.

That malicious script can do real damage. It can steal session cookies, hijack a logged-in user's session, redirect visitors to phishing pages, or deface your site. Stored XSS — where the payload is saved in your database (for example, in a comment) — is especially dangerous because it hits every visitor who loads the page.

The good news: XSS is preventable. Follow these three rules. First, never trust user input — validate it on the server and escape it when rendering HTML, so browsers treat it as text, not code. Second, use a strong Content Security Policy (CSP) header, which tells browsers exactly which scripts are allowed to run. Third, keep your CMS, plugins, and themes updated — most XSS bugs reported in the wild are exploited through outdated third-party code.

You don't need to be a security expert to find out whether your site is exposed. A free vulnerability scan is a quick first step: run a free scan of your site at Vulnerability Tools to check for XSS and dozens of other common issues before attackers do. Make scanning part of your routine, and XSS goes from an invisible risk to a handled one.