Stop XSS Attacks Before They Strike
Content Security Policy violations reveal attempted attacks and misconfigurations. Monitor them in real-time to protect your users and harden your defenses.
The Problem
XSS Remains the Web's Most Dangerous Vulnerability
Cross-site scripting (XSS) consistently ranks among the most exploited web vulnerabilities. Attackers use it to steal user credentials, hijack sessions, and inject malware — all without your users knowing anything is wrong.
The threat has evolved. Supply chain attacks like Magecart compromise trusted third-party scripts to skim payment card data directly from checkout pages. Your site loads dozens of external scripts for analytics, ads, and widgets — each one a potential attack vector.
Without visibility into what scripts actually execute on your pages, attacks go undetected. You find out weeks later when customers report fraudulent charges or when auditors discover the breach.
The Solution
Content Security Policy: Your Browser's Built-In Defense
Content Security Policy (CSP) is a W3C standard that lets you define exactly which sources your site trusts for scripts, styles, images, and other resources. Browsers enforce these rules automatically — blocking anything not on your allowlist.
CSP is supported by 93.6% of browsers worldwide, including Chrome 14+, Firefox 4+, Safari 6+, and Edge 12+. It's a mature, battle-tested defense that's already built into your users' browsers.
Key directives control different resource types: script-src for JavaScript, style-src
for CSS, img-src for images. You can allow specific origins, block inline scripts, and require
Subresource Integrity for third-party resources.
Configuration is pure HTTP headers — no JavaScript SDK or build changes required. Add a
Content-Security-Policy header to your server responses, and browsers start enforcing your rules
immediately.
The Challenge
But CSP Alone Leaves You Flying Blind
CSP is powerful, but it has a critical weakness: violations are invisible. When a browser blocks a script, the only trace is a message in the developer console — invisible to security teams, compliance officers, and anyone not actively debugging.
When you do try to collect CSP reports, you're hit with a flood of noise. Browser extensions, ad blockers, and ISP-injected toolbars trigger violations that look identical to real attacks. At high-traffic sites, over 90% of CSP reports are false positives from user-installed software.
Teams hesitate to deploy strict CSP because misconfiguration breaks legitimate features. You want to tighten
security, but fear blocking your own scripts. Content-Security-Policy-Report-Only mode helps — but
generates data you need specialized infrastructure to collect.
Meanwhile, PCI DSS 4.0 now mandates script monitoring on payment pages. Compliance teams need proof that you're detecting and responding to unauthorized script execution. But where's the data?
The Answer
The Reporting API Makes CSP Violations Visible
We support both report-to and report-uri directives for complete browser coverage.
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Intelligent Noise Filtering
- Auto-filter browser extension violations from
chrome-extension://,moz-extension://, andsafari-extension://. See only real threats, not false positives from user-installed software. -
Real-Time Visibility
- Route violations to AppSignal, webhooks, or Google Chat instantly. See blocked attacks the moment they happen, and catch overblocking before users complain about broken features.
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Safe Policy Testing
- Deploy CSP in Report-Only mode with confidence. Test strict policies against real traffic, identify what would break, and tighten security incrementally.
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Compliance Ready
- Meet PCI DSS 4.0 requirements for script monitoring on payment pages. Maintain an audit trail of blocked violations and demonstrate active security governance.
Ready to Monitor CSP Violations?
Capture Content Security Policy violations and route them to your existing tools. Setup takes minutes.