How To Prevent XSS Attacks On WYSIWYG Editors

WYSIWYG editors are now an integral part of many websites. They enable users to comment on posts, type email messages, enter feedback, and more.

Many WYSIWYG editors also allow users to enter HTML or Markdown directly in the editor window.

While WYSIWYG HTML editors are a great feature of many websites, their design makes them vulnerable to attacks, including cross-site scripting or XSS attacks.

No matter which programming language or framework you use, there is always the chance of an XSS attack on your WYSIWYG editor. This includes Java, React, Angular, Javascript, Django WYSIWYG editor, and more.

This blog will explain how an XSS attack on your WYSIWYG editor can occur. We also have helpful guidelines for the prevention of these attacks.

What Is A Cross-Site Scripting (XSS) Attack?

Cross-site scripting, or XSS, is a vulnerability of computer systems, mostly web applications, that exposes them to potential attacks and hacks.

An XSS attack occurs when an attacker injects code into a web application or website that a user can trust.

This code is sent to the user/client’s machine when the web application transmits data. Next, the malicious code or script executes on the client’s machine, generally in the web browser.

An XSS attack can result in anything, ranging from showing a harmless advertisement or message to stealing essential data of a user or corrupting their entire system.

Why Are WYSIWYG Editors Vulnerable To XSS Attacks?

There are several ways an XSS attack occurs on a WYSIWYG HTML editor. A WYSIWYG editor allows users to enter and format rich text directly in their browser’s window.

While this is an excellent feature of a WYSIWYG editor, the rich content entered by a user can lead to an XSS attack.

The WYSIWYG editor allows attackers to inject code through various injection points. These include adding web links, inserting images, adding videos, ALT tags, and more to the rich text being added and edited in a WYSIWYG editor. A few are explained below.

Is XSS Possible Using Image Creation In WYSIWYG Editor?

It is possible to create an XSS attack by inserting images in WYSIWYG editors. HTML allows users to insert images in a document by using the <img src=””> tag. The src attribute lets users specify the address of the image file.

The attacker can abuse this feature by injecting malicious JavaScript code into the src attribute’s value. JavaScript can also be embedded in an SVG image file and later executed at the client’s end.

Do CSS Expressions Contribute To XSS Vulnerability?

CSS expressions also allow attackers to inject malicious code into a client’s system. Many WYSIWYG editors support styling content using CSS. For example, they can set the color and font of the text.

An attacker can exploit this feature by injecting malicious JavaScript code into the CSS expressions. Many old browsers execute the CSS expressions and become vulnerable to XSS attacks.

Is XSS Possible Through Link Creation In Rich Text Editor?

Indeed, an XSS attack is possible using the link creation capability of a rich text WYSIWYG editor. To create a hyperlink in HTML the tag <a href= “”> is used followed by the closing tag </a>.

The href parameter lets a user specify a URL for the hyperlink. An attacker can exploit this feature by identifying a JavaScript URI instead of a valid URL. For example, javascript:some_code will allow some_code to get executed. The attacker can also use data URI or VbScript URI to execute malicious code on the user’s machine.

What Are The Dangers Posed By XSS Attacks On WYSIWYG Editors?

An XSS attack can lead to dangerous and severe consequences. For example, see the list below:

• • Hackers can execute malicious code at the client end and cause harm to the system. For example, they can delete files, copy illegal files to the system, and more.
  • The attacker can change the appearance of a web page shown to a user.
  • A hacker or attacker can access sensitive data belonging to the user. This data includes credit card data, phone numbers, other contacts, and more.
  • The attacker can perform a phishing attack, allowing them to steal a user’s data.
  • An attacker can even gain control and administrative rights of a website.

How Can I Prevent XSS Attacks On WYSIWYG Editors?

Here are a few tips for developers of WYSIWYG editors who want to integrate a WYSIWYG HTML-rich text editor in their web app or on their website. Alternatively, we suggest you use a third-party solution.

What Are Some Tips For Developers?

Developers can ensure that the WYSIWYG HTML editor is safe from XSS vulnerability. Here are a few tips:

• • If a user wants to create a link, it should always start with HTTP or HTTPS. Your code should parse and check the link to ensure it is valid and does not contain any executable code.
  • If the WYSIWYG editor allows users to upload files, the software should also check and verify the file before upload. The software should also run an anti-virus check on the file.
  • Developers should not allow users to upload SVG images as an attacker can execute JavaScript through an SVG image.
  • Developers should not allow users to style content using executable CSS expressions.

Is It A Good Idea To Use A Third Party Off-The-Shelf Solution?

One of the best ways to prevent XSS attacks on WYSIWYG editors is to use a third-party rich text editor. Instead of building your own HTML editor, using a tried and tested, professionally built WYSIWYG editor for your web page or app is best.

As an example of a third-party solution, you can try out Froala. The development teams of Froala and other WYSIWYG editors ensure that their editors are up-to-date and safe from XSS and other attacks. All you need to do is keep the latest version of the software at your end.

There are several advantages of using third-party paid solutions. Any time a user reports a new type of attack, the development team works to resolve the problem and releases a patch or the latest version of the software.

With these constant updates, you can rest assured that your WYSIWYG editor is safe from XSS vulnerabilities.

What Are The Key Takeaways?

WYSIWYG editors are very popular in web apps and internet websites. They allow users to create rich text content easily and quickly. However, these WYSIWYG HTML editors are vulnerable to XSS attacks.

There are different types of XSS attacks. One of the best possible solutions to avoid XSS attacks is to use a third-party solution.

Third-party developers constantly release software updates that counter all types of new XSS attacks. Keeping the latest version or update of the software can help to keep your system safe.