CLIENT-SIDE SECURITY
A practical map of browser-side risk
Understand what executes, what it can reach, what changed, and how your team can respond.
What client-side security covers
Client-side security protects the code, data, and behavior that exist after a page reaches a visitor's browser. It connects secure development with third-party governance, runtime observation, policy enforcement, change detection, and incident response.
Four questions to answer
- Which first-party and third-party resources execute?
- Which browser capabilities, data, and destinations can they reach?
- How does their content or behavior change over time?
- Can the team investigate and contain unsafe behavior quickly?
Build the foundation
Use these guides in sequence or go directly to the risk your team is investigating.
Client-Side Security
What Is Client-Side Security? Risks, Attacks, and Best Practices
Learn what client-side security protects, how browser attacks work, why third-party JavaScript creates risk, and which controls secure modern web applications.
Client-Side Security
Types of Client-Side Attacks: 12 Browser Threats to Know
Explore 12 common client-side attacks, how they reach the browser, what warning signs to investigate, and which controls can reduce the risk.
Client-Side Security
Third-Party JavaScript Monitoring: Uptime, Updates, and Behavioral Drift
Learn how to monitor third-party script availability, performance, update frequency, dependency changes, and unexpected behavior in the browser.
Supply Chain Security
OWASP Subresource Integrity (SRI) Guide: Securing the Supply Chain
An authoritative primer on implementing Subresource Integrity (SRI) to prevent third-party script injection, Magecart attacks, and unauthorized CDN modifications.
Turn knowledge into a security program
Connect browser visibility to ownership, policy, response, and evidence across the pages that matter most.
Manage the client-side attack surface
Inventory resources, capabilities, destinations, and changes across production pages.
Govern third-party scripts
Assign ownership, validate business purpose, and control provider behavior over time.
Reduce browser supply-chain risk
Detect dependency drift and unexpected behavior from trusted external resources.
Protect payment journeys
Monitor scripts and data access on payment pages for indicators of digital skimming.
Client-side security questions
How is client-side security different from application security?
Application security covers the broader software lifecycle and application stack. Client-side security focuses on code and behavior inside the user's browser, including third-party scripts, browser storage, data access, network destinations, and runtime changes.
Is client-side security only about cross-site scripting?
No. Cross-site scripting is one risk, but client-side security also covers compromised vendors, malicious dependencies, tag-manager changes, payment skimming, unsafe browser storage, deceptive interfaces, and unauthorized data collection.
Why are third-party scripts a security concern?
Third-party scripts execute in the browser with the permissions the page gives them. They may access page content, browser APIs, storage, form data, and network destinations, and their code can change without a first-party deployment.
What should a client-side security program measure?
A useful program tracks resource inventory, provider ownership, sensitive capabilities, network destinations, content and behavior changes, policy violations, affected pages, response time, and evidence retained for review.