Contain XSS Risks
Reduce the risk of cross-site scripting attacks by restricting scripts and or requests.
Stop Data Exfiltration From Any Web App
The threat of Cross-Site Scripting (XSS) is well-known, but today’s security challenges run much deeper. Your attack surface now includes legacy systems you can't patch and third-party applications you don't control—all forming a complex ecosystem of code and dependencies.
This is where traditional defenses break down.
A Content Security Policy (CSP) is a crucial layer, but it's notoriously difficult to implement correctly and isn't available everywhere.
- You can't modify the CSP headers of the third-party SaaS apps your organization relies on.
- It's often impossible to patch or modify the code of legacy internal applications.
- This leaves you relying on the vendor to fix vulnerabilities—a slow process you have no control over.
When you can't control the server, you can't set the policy. Your organization is left exposed.
Webfuse Gives You Control—Without Touching the Backend
Webfuse applies outbound domain allowlists at the session level, ensuring compromised apps can’t leak data to unauthorized domains even if a malicious script executes.
Watch the full breakdown: In this 5-minute session, see exactly how Webfuse contains these threats and gives you control over any application.
How Webfuse Solves This: The Lockdown App
Using Webfuse’s Lockdown App, you can:
- Create a Granular Allowlist: Define precisely which domains your applications are permitted to communicate with (e.g., *.example.com, api.service.com). Learn how to create detailed rules in this article.
- Block Unauthorized Requests: Instantly prevent any navigation, script load, or API call to an unlisted domain. Any script attempting to violate this policy is automatically blocked.
- Apply Policies Instantly: Enforce these rules at the Virtual Web Session level without a single backend change.
Key Benefits
- Reduce the Impact of XSS Attacks: A rogue script may execute, but it can't exfiltrate data or communicate with an attacker's server. Its blast radius is contained.
- Secure Your Software Supply Chain: Drastically limit the risk from compromised third-party scripts by controlling exactly where they can send data.
- Protect Users of Any App: Apply robust security to SaaS platforms, vendor portals, and legacy applications—even those you don't host.
Sign Up & Get Started
Launch a SPACE with outbound domain restrictions in minutes.
FAQ
Can I use Webfuse to prevent scripts from running inside a web app?
No, Webfuse doesn’t alter a site’s internal JS behavior directly. Instead, it restricts external communications by applying domain-level restrictions—so even if malicious scripts run, they cannot exfiltrate data.
Do I need developer access to the original app to apply restrictions?
Not at all. Webfuse applies the restrictions via Virtual Web Sessions—no backend or server-side access is needed.
Can I combine this with a Content Security Policy?
Yes! You can inject CSP headers via the Custom Headers App to add another layer of protection on top of domain allowlisting.
What happens if the app tries to call an unapproved domain?
The request will be blocked within the session, and depending on the browser, users may see a generic failure or nothing at all—ensuring no data leaves your allowed scope.
