A recent vulnerability discovered in the joyqi/hyper-down package platform, precisely in the module of parse markdown, has led to cases of Cross-site Scripting (XSS) attacks. The vulnerability affects the versions starting from .. and results from inadequately filtered href attributes. This post aims to discuss the exploit's details and provide snippets of code that demonstrate the issue, as well as links to original references that researchers can use to look deeper into the problem. Through this post, you will understand the severity of the issue and how to prevent or address it in your project.

Vulnerability Overview

Software: joyqi/hyper-down

Exploit Details

Cross-site Scripting, otherwise known as XSS, refers to a security vulnerability where attackers inject malicious scripts into a vulnerable application. An XSS attack typically exploits a weakness in user input sanitization, allowing hackers to put unsafe content like JavaScript code into input forms.

In the case of joyqi/hyper-down's vulnerability, the parse markdown module fails to filter the href attribute effectively. Here's a snippet of the flawed code that inadvertently enables XSS attacks:

function parseMarkdownLink(href, title) {
    // Insecure code: Not filtering 'href' attribute properly
    var result = '<a href="' + href + '"';

As a consequence of this inappropriate filtering, an attacker can inject malicious scripts into the href attribute. For example:

[Click here](javascript:alert('XSS'))

Given the situation, when the parseMarkdownLink function processes this input, it generates the following insecure output:

<a href="javascript:alert('XSS')">Click here</a>

This lack of filtering, among other things, can lead users to visit malicious websites, leak sensitive information, or unknowingly take part in harmful activities via the vulnerable application.


- CVE-2022-25849 NVD
- joyqi/hyper-down GitHub Repository
- Understanding Cross-site Scripting (XSS)


Developers using vulnerable versions are strongly recommended to update the joyqi/hyper-down library to the latest version with security patches. It is crucial to make sure proper input validation and sanitization mechanisms are in place, particularly when handling user-supplied data.

Additionally, developers and operators should also adopt security best practices, such as implementing a Content Security Policy (CSP) within their applications to reduce the risk of XSS attacks.

In Summary

An XSS vulnerability in joyqi/hyper-down's parse markdown module poses a critical risk to users of the package starting from version ... Developers must update the package to the latest version with security fixes and apply the mitigation steps mentioned above to prevent any potential exploitation of this vulnerability. By being proactive and implementing the necessary measures, developers can safeguard their applications and promote user trust in their projects.


Published on: 10/26/2022 05:15:00 UTC
Last modified on: 11/03/2022 13:59:00 UTC