The Invisible Threat
Imagine waking up to find your website defaced overnight, customers locked out, or their data compromised. This was the reality for British Airways in 2018, when a vulnerability similar to Cross-Site Scripting (XSS) allowed attackers to siphon customer data, costing the airline over $230 million.Understanding XSS
Cross-Site Scripting comes in three forms: reflected, stored, and DOM-based XSS. Each has unique traits but shares a common goal — injecting malicious scripts to compromise user data.Reflected XSS
Reflected XSS often targets input fields like search boxes. When you search, the site 'reflects' your input back, but if it doesn't sanitize it, hackers can input scripts instead of text.Example: On a vulnerable search page, instead of 'cats', a hacker inputs . If the site reflects this input directly, the script runs in the user's browser.
Stored XSS
Stored XSS is more insidious, saving the script on the server itself, waiting for users to load the page.Example: A forum post with executes every time someone views the post, affecting multiple users.
DOM-Based XSS
DOM-based XSS stems from client-side script vulnerabilities.Example: A site's JavaScript might directly include user input into the DOM. A hacker could manipulate the URL, injecting a payload like #, which the script processes unsafely.
Real-World Impact
XSS can lead to damaging outcomes:- Session Hijacking: Attackers steal session cookies, impersonating users.
- Defacement: Hackers alter the website, damaging your brand.
- Credential Theft: Users might be tricked into entering sensitive information.
How AttackVector Tests for XSS
AttackVector's AI-powered pentest module simulates real-world attacks to identify XSS vulnerabilities. The tool focuses on input fields, URL parameters, and client-side scripts, flagging potential vectors for exploitation.Testing for XSS:
- 1Use tools like Burp Suite or OWASP ZAP to intercept requests.
- 2Inject payloads like
into input fields. - 3Analyze responses to see if scripts execute.
Prevention Techniques
Input Validation
Validate and sanitize all user inputs. Reject anything resembling code.
Output Encoding
Encode data before rendering on the page. Use libraries like OWASP Java Encoder.Content Security Policy (CSP)
Implement CSP headers to restrict which scripts can execute.Pitfall to Avoid: Never rely solely on blacklisting. Hackers can obfuscate payloads to bypass simple filters.