---
title: "Out of Band XSS"
description: "HawkScan test information for plugin 40031: Out of Band XSS"
url: https://docs.stackhawk.com/vulnerabilities/40031/
---

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# Out of Band XSS

###### Reference

- **Plugin ID:** 40031
- [**CWE:** 79](https://cwe.mitre.org/data/definitions/79.html)
- **Risk:** High
- **Type:** Active
- **Category:**

### Remediation

1. **Input validation**: Implement strict input validation for all user-supplied data using allowlists and sanitization.
2. **Output encoding**: Encode all user data before outputting to HTML, JavaScript, CSS, or other contexts.
3. **Content Security Policy**: Implement CSP headers to restrict script execution and prevent XSS attacks.
4. **Use secure frameworks**: Utilize web frameworks with built-in XSS protection and auto-escaping templates.
5. **Regular security testing**: Conduct periodic security assessments to identify and remediate XSS vulnerabilities.

### About

Out-of-band Cross-Site Scripting (XSS) is a vulnerability where malicious scripts are injected into web applications and executed in users' browsers outside the normal request-response flow. This attack compromises the trust relationship between users and websites, allowing attackers to steal sensitive data, hijack sessions, or perform unauthorized actions on behalf of victims.

### Risks

**High** XSS attacks can lead to session hijacking, credential theft, data exfiltration, malware distribution, defacement, and complete compromise of user accounts and application security.