The CSP Reality Check
After implementing CSP across dozens of client projects, I've learned that the theory and practice of Content Security Policy are worlds apart. Here's what nobody tells you about real-world CSP implementation.
The Third-Party Script Nightmare
Every client wants Google Analytics, Facebook Pixel, and a dozen other tracking scripts. The problem? Most of them load additional scripts dynamically, which breaks your carefully crafted CSP policy.
Real-World CSP Challenges
- Analytics scripts that load more scripts (looking at you, Google Tag Manager)
- Payment processors that require specific domains and inline scripts
- CDN resources that change URLs frequently
- Social media widgets that break with strict policies
- A/B testing tools that inject code dynamically
The WordPress Plugin Problem
WordPress plugins are the bane of CSP implementation. I've seen plugins that:
Plugin Issues I've Encountered
- Load external scripts without checking CSP policies
- Use inline styles and scripts everywhere
- Include third-party resources from unverified sources
- Break when you add security headers
- Have no documentation about CSP compatibility
My CSP Implementation Strategy
After many failed attempts, I developed a systematic approach to CSP implementation:
The Step-by-Step Process
- Start with report-only mode and monitor for a week
- Document every violation and categorize them
- Create a whitelist of legitimate resources
- Implement nonces for inline scripts that can't be avoided
- Test with real users, not just developers
- Set up monitoring to catch new violations
The Nonce vs Hash Dilemma
When you can't avoid inline scripts, you have two options: nonces or hashes. I prefer nonces because they're more flexible, but they require server-side implementation. Hashes are easier but break every time the content changes.
Client Education is Crucial
The biggest challenge isn't technical - it's explaining to clients why their favorite plugin breaks their security policy. I've learned to:
Client Communication Tips
- Show them the security benefits with real examples
- Explain the trade-offs between security and functionality
- Provide alternatives when plugins don't work
- Set clear expectations about what's possible
- Document everything for future reference
The Monitoring Revelation
The game-changer was implementing proper CSP monitoring. Without it, you're flying blind. With it, you can see exactly what's being blocked and why, making CSP implementation much more manageable.