CSP is one of the most elaborate security policies in modern browsers. Besides acting as a second line of defense against XSS, CSP offers control over various types of content, outgoing connections, and the application's behavior. In this article, we elaborate on these features and provide you with a prioritized CSP deployment guide that will help you configure CSP in production.

24 May 2022 Security Policies Browser Security, Content Security Policy (CSP), XSS

The recommended best practice for modern CSP policies relies on hashes, nonces, and 'strict-dynamic'. Unfortunately, these features conflict with modern SPAs. This article proposes three concrete strategies to deploy secure CSP policies for SPAs. The first relies on a simple policy allowing 'self', which is acceptable under certain circumstances. The second strategy enables CSP hashes by rewriting the main page to use a script loader. The third strategy inserts nonces into a dynamically served main page.

11 April 2022 Security Policies Browser Security, Content Security Policy (CSP), XSS

Content Security Policy (CSP) started as a simple defense but quickly evolved into a complex security policy. This article investigates how to build an effective CSP policy to counter XSS vulnerabilities. Concretely, we use step-by-step examples to highlight bypasses against CSP and examine how to use nonces, hashes, and 'strict-dynamic' to build a robust CSP policy for modern applications.

13 December 2021 Security Policies Browser Security, Content Security Policy (CSP), XSS

XSS vulnerabilities remain a top threat to any HTML-based web application. In fact, 75% of web vulnerabilities in Google's reward program are XSS vulnerabilities! Fortunately, built-in platform defenses such as Content Security Policy and Trusted Types equip us with the tools to tackle XSS. In this article, we briefly look at modern XSS vulnerabilities, followed by a detailed look at using Trusted Types policies to mitigate such vulnerabilities. In the end, we provide you with a list of concrete developer guidelines to apply Trusted Types in your projects.

15 June 2021 Security Policies Browser Security, Content Security Policy (CSP), XSS, Trusted Types

Frame-based attacks such as clickjacking and UI redressing may be obscure, but they are (still) very real. They even threaten APIs, which have nothing to do with iframes and web pages. This article gives an overview of the threats, discusses recent changes in framing restriction mechanisms, and provides concrete recommendations to secure modern web applications.

15 September 2020 Security Policies Browser Security, X-Frame-Options (XFO), Content Security Policy (CSP)