Want to learn more about OAuth 2.0 and OpenID Connect?
Save yourself days of digging through dozens of specs with this online courseMore information
Security is often about small nuances. These articles dive deeper into various security topics, providing concrete guidelines and advice. They address common questions and misconceptions on building secure applications.
Articles are also available as an RSS / Atom feed
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.
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.
In this article, we investigate the security properties of refresh tokens in the browser. We investigate why frontend web applications need refresh token rotation and what we gain by using refresh token rotation. Next, we dive into concrete attack scenarios that bypass refresh token rotation and discuss how sensitive SPAs should use a backend-for-frontend to secure tokens.
A Cross-Site Scripting (XSS) vulnerability can and will lead to the full compromise of a frontend application. An XSS vulnerability allows the attacker to control the application in the user's browser, extract sensitive information, and make requests on behalf of the application. Modern frameworks come with built-in defenses against XSS, but how far do they really go? In this article, we look at Angular's built-in XSS defenses, along with insecure coding patterns that inadvertently bypass these protections.
Traditionally, OAuth 2.0 applications rely on iframes to silently obtain tokens in the background while the application remains running in the foreground. With the ongoing efforts to block third-party cookies, these flows become increasingly unreliable. Use the new version of the Flow Simulator to visualize the effects of third-party cookie blocking in Brave and Safari.
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.
Have you ever heard of the device flow, or the OAuth 2.0 Device Authorization Grant? If not, make sure you keep reading, as the device flow is pretty awesome to support an ever-growing group of applications. If you already know about the device flow, you should skip to the second half of the article, where we discuss the details and the surprising amount of security benefits.
I often need to explain the different steps in OAuth 2.0 and OpenID Connect flows, for example during a training or consulting session. Illustrating the numerous steps with a real-world application is always challenging, especially since many of the requests are invisible to the user. That's why I built the Flow Simulator, which allows you to walk through a flow step by step, while visualizing all the relevant details. Keep reading to learn all about the publicly available Flow Simulator.
Everyone who first learns about OAuth 2.0 and OpenID Connect is confused. There are dozens of specifications with uncommon terminology and hard-to-understand scenarios. That's why I am excited to announce this free introductory course, which is the perfect starting point for your journey into OAuth 2.0 and OpenID Connect. More details are available in this article.
Preventing XSS in React is manageable when you stay within the boundaries of the framework, but becomes hard once you step out of React's safe zone. In this article, we take a closer look at escape hatches and component parsers and all the reasons you should avoid them. Read on to discover the next level of XSS in React applications.
Dynamically rendering benign HTML code in React requires the use of
dangerouslySetInnerHTML. That is not a naming mistake. This property is dangerous, and using it carelessly will create XSS vulnerabilities in your application. In this article, we discuss why the property is there, how you can use it, and how the Signal messenger misused it. This article is the second in a series of three, and a must-read for every React developer.
Good audio for virtual presentations is absolutely critical. Even before the new world of 2020, I was delivering remote training and recording videos, so I invested in a decent audio setup. Since the Corona pandemic coincided with the birth of our third child, training from home sure became a totally new challenge. To make that as comfortable as possible, I built myself a standing desk and added a dedicated camera to the setup. A few people asked about my setup, I decided to provide a bit more details in this article.
A Cross-Site Scripting (XSS) vulnerability can and will lead to the full compromise of a frontend application. An XSS vulnerability allows the attacker to control the application in the user's browser, extract sensitive information, and make requests on behalf of the application. Modern frameworks come with built-in defenses against XSS, but how far do they really go? In this article series, we look at how React prevents XSS, but also how its shortcomings leave a lot in the hands of a developer. This article is the first in a series of three.
About a year ago, the OAuth 2.0 Implicit flow became deprecated. That decision caused a lot of confusion and frustration. In this article, we analyze the different OAuth 2.0 flows to find out why the OAuth working group made that decision. Read on to find out about current best practices for using OAuth 2.0 in modern web applications.
Single Page Applications can use refresh tokens in the browser. Yes, you read that right. This new development is awesome, because it makes access token renewal much more elegant. However, refresh tokens in the browser require additional security measures, such as refresh token rotation. We discuss the pros and cons of refresh token rotation, along with the potential dangers. In the end, you will find five strategies you can use to secure your tokens in your web frontends better.
Most developers are afraid of storing tokens in LocalStorage due to XSS attacks. While LocalStorage is easy to access, the problem actually runs a lot deeper. In this article, we investigate how an attacker can bypass even the most advanced mechanisms to obtain access tokens through an XSS attack. Concrete recommendations are provided at the end.
URL parameters are straightforward to send information along in a request. Decades ago, we already used them to transport session identifiers, and today, many applications still use them for all kinds of purposes. But are URL parameters secure? What alternatives are there? Keep reading to find out more.
In spite of the popularity of JWTs, their security properties are often unknown or misunderstood. How do you choose the signature scheme for a JWT? What other properties should you verify before trusting a JWT? How do you handle key rotation and key management? Read on for a deep-dive into JWT security.
Dr. Philippe De Ryck
Hi, I'm Philippe, and I help developers protect companies through better web security. As the founder of Pragmatic Web Security, I travel the world to teach practitioners the ins and outs of building secure software.
Talks and workshops
Getting security right is all about knowledge. I strongly believe in sharing that knowledge to move forward as a community. Among my resources, you can find developer cheat sheets, recorded talks, and extensive slide decks.
Subscribe to the Pragmatic Web Security mailing list to stay up to date on the latest activities and resources.