Previous Post A style guide generator for Vue components with a living style guide. Apply Vuex Store and v-if to a Vue CLI Project Read More. My LaTex Cheat Sheet Read More. How to Resolve ESXi RealTek NIC Incompatibility. Are you targeting the correct property: Updating a property in Vuex state. When your Vue application starts to become more complex, and you have things that are named similarly, and perhaps more nesting than is healthy in your data structures, it can be easy to target the incorrect property when you are mutating the state.
This is the docs for Vuex 4, which works with Vue 3. If you're looking for docs for Vuex 3, which works with Vue 2, please check it out here.
Vuex is a state management pattern + library for Vue.js applications. It serves as a centralized store for all the components in an application, with rules ensuring that the state can only be mutated in a predictable fashion.
# What is a 'State Management Pattern'?
Let's start with a simple Vue counter app:
It is a self-contained app with the following parts:
- The state, the source of truth that drives our app;
- The view, a declarative mapping of the state;
- The actions, the possible ways the state could change in reaction to user inputs from the view.
This is a simple representation of the concept of 'one-way data flow':
However, the simplicity quickly breaks down when we have multiple components that share a common state:
- Multiple views may depend on the same piece of state.
- Actions from different views may need to mutate the same piece of state.
For problem one, passing props can be tedious for deeply nested components, and simply doesn't work for sibling components. For problem two, we often find ourselves resorting to solutions such as reaching for direct parent/child instance references or trying to mutate and synchronize multiple copies of the state via events. Both of these patterns are brittle and quickly lead to unmaintainable code.
So why don't we extract the shared state out of the components, and manage it in a global singleton? With this, our component tree becomes a big 'view', and any component can access the state or trigger actions, no matter where they are in the tree!
By defining and separating the concepts involved in state management and enforcing rules that maintain independence between views and states, we give our code more structure and maintainability.
This is the basic idea behind Vuex, inspired by Flux, Redux and The Elm Architecture. Unlike the other patterns, Vuex is also a library implementation tailored specifically for Vue.js to take advantage of its granular reactivity system for efficient updates.
If you want to learn Vuex in an interactive way you can check out this Vuex course on Scrimba, which gives you a mix of screencast and code playground that you can pause and play around with anytime.
# When Should I Use It?
Vuex helps us deal with shared state management with the cost of more concepts and boilerplate. It's a trade-off between short term and long term productivity.
If you've never built a large-scale SPA and jump right into Vuex, it may feel verbose and daunting. That's perfectly normal - if your app is simple, you will most likely be fine without Vuex. A simple store pattern may be all you need. But if you are building a medium-to-large-scale SPA, chances are you have run into situations that make you think about how to better handle state outside of your Vue components, and Vuex will be the natural next step for you. There's a good quote from Dan Abramov, the author of Redux:
Flux libraries are like glasses: you’ll know when you need them.
You’re browsing the documentation for v2.x and earlier. For v3.x, click here.
Reporting Vulnerabilities
When a vulnerability is reported, it immediately becomes our top concern, with a full-time contributor dropping everything to work on it. To report a vulnerability, please email [email protected].
While the discovery of new vulnerabilities is rare, we also recommend always using the latest versions of Vue and its official companion libraries to ensure your application remains as secure as possible.
Rule No.1: Never Use Non-trusted Templates
The most fundamental security rule when using Vue is never use non-trusted content as your component template. Doing so is equivalent to allowing arbitrary JavaScript execution in your application - and worse, could lead to server breaches if the code is executed during server-side rendering. An example of such usage:
Vue templates are compiled into JavaScript, and expressions inside templates will be executed as part of the rendering process. Although the expressions are evaluated against a specific rendering context, due to the complexity of potential global execution environments, it is impractical for a framework like Vue to completely shield you from potential malicious code execution without incurring unrealistic performance overhead. The most straightforward way to avoid this category of problems altogether is to make sure the contents of your Vue templates are always trusted and entirely controlled by you.
What Vue Does to Protect You
HTML content
Whether using templates or render functions, content is automatically escaped. That means in this template:
if
userProvidedString
contained:then it would be escaped to the following HTML:
thus preventing the script injection. This escaping is done using native browser APIs, like
textContent
, so a vulnerability can only exist if the browser itself is vulnerable.Attribute bindings
Similarly, dynamic attribute bindings are also automatically escaped. That means in this template:
Vuex Cheat Sheet
if
userProvidedString
contained:then it would be escaped to the following HTML:
Vuex Cheat Sheet Pdf
thus preventing the close of the
title
attribute to inject new, arbitrary HTML. This escaping is done using native browser APIs, like setAttribute
, so a vulnerability can only exist if the browser itself is vulnerable.Potential Dangers
In any web application, allowing unsanitized, user-provided content to be executed as HTML, CSS, or JavaScript is potentially dangerous, so should be avoided wherever possible. There are times when some risk be acceptable though. Google pc version.
For example, services like CodePen and JSFiddle allow user-provided content to be executed, but it’s in a context where this is expected and sandboxed to some extent inside iframes. In the cases when an important feature inherently requires some level of vulnerability, it’s up to your team to weigh the importance of the feature against the worst-case scenarios the vulnerability enables.
Injecting HTML
As you learned earlier, Vue automatically escapes HTML content, preventing you from accidentally injecting executable HTML into your application. However, in cases where you know the HTML is safe, you can explicitly render HTML content:
- Using a template:
- Using a render function:
- Using a render function with JSX:
Note that user-provided HTML can never be considered 100% safe unless it’s in a sandboxed iframe or in a part of the app where only the user who wrote that HTML can ever be exposed to it. Additionally, allowing users to write their own Vue templates brings similar dangers.
Injecting URLs
In a URL like this:
There’s a potential security issue if the URL has not been “sanitized” to prevent JavaScript execution using
javascript:
. There are libraries such as sanitize-url to help with this, but note:If you’re ever doing URL sanitization on the frontend, you already have a security issue. User-provided URLs should always be sanitized by your backend before even being saved to a database. Then the problem is avoided for every client connecting to your API, including native mobile apps. Also note that even with sanitized URLs, Vue cannot help you guarantee that they lead to safe destinations.
Injecting Styles
Looking at this example:
let’s assume that
sanitizedUrl
has been sanitized, so that it’s definitely a real URL and not JavaScript. With the userProvidedStyles
, malicious users could still provide CSS to “click jack”, e.g. styling the link into a transparent box over the “Log in” button. Then if https://user-controlled-website.com/
is built to resemble the login page of your application, they might have just captured a user’s real login information.You may be able to imagine how allowing user-provided content for a
<style>
element would create an even greater vulnerability, giving that user full control over how to style the entire page. That’s why Vue prevents rendering of style tags inside templates, such as:To keep your users fully safe from click jacking, we recommend only allowing full control over CSS inside a sandboxed iframe. Alternatively, when providing user control through a style binding, we recommend using its object syntax and only allowing users to provide values for specific properties it’s safe for them to control, like this:
Injecting JavaScript
We strongly discourage ever rendering a
<script>
element with Vue, since templates and render functions should never have side effects. However, this isn’t the only way to include strings that would be evaluated as JavaScript at runtime.Every HTML element has attributes with values accepting strings of JavaScript, such as
onclick
, onfocus
, and onmouseenter
. Binding user-provided JavaScript to any of these event attributes is a potential security risk, so should be avoided.Note that user-provided JavaScript can never be considered 100% safe unless it’s in a sandboxed iframe or in a part of the app where only the user who wrote that JavaScript can ever be exposed to it.
Sometimes we receive vulnerability reports on how it’s possible to do cross-site scripting (XSS) in Vue templates. In general, we do not consider such cases to be actual vulnerabilities, because there’s no practical way to protect developers from the two scenarios that would allow XSS:
- The developer is explicitly asking Vue to render user-provided, unsanitized content as Vue templates. This is inherently unsafe and there’s no way for Vue to know the origin.
- The developer is mounting Vue to an entire HTML page which happens to contain server-rendered and user-provided content. This is fundamentally the same problem as #1, but sometimes devs may do it without realizing. This can lead to possible vulnerabilities where the attacker provides HTML which is safe as plain HTML but unsafe as a Vue template. The best practice is to never mount Vue on nodes that may contain server-rendered and user-provided content.
Best Practices
The general rule is that if you allow unsanitized, user-provided content to be executed (as either HTML, JavaScript, or even CSS), you might be opening yourself up to attacks. This advice actually holds true whether using Vue, another framework, or even no framework.
Beyond the recommendations made above for Potential Dangers, we also recommend familiarizing yourself with these resources:
Webstorm pycharm download. Then use what you learn to also review the source code of your dependencies for potentially dangerous patterns, if any of them include 3rd-party components or otherwise influence what’s rendered to the DOM.
Backend Coordination
HTTP security vulnerabilities, such as cross-site request forgery (CSRF/XSRF) and cross-site script inclusion (XSSI), are primarily addressed on the backend, so aren’t a concern of Vue’s. However, it’s still a good idea to communicate with your backend team to learn how to best interact with their API, e.g. by submitting CSRF tokens with form submissions.
Server-Side Rendering (SSR)
There are some additional security concerns when using SSR, so make sure to follow the best practices outlined throughout our SSR documentation to avoid vulnerabilities.
← Server-Side RenderingReactivity in Depth →
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