Executive Summary

This vulnerability is a Cross-Site Scripting (XSS) bypass in Horilla HRM version 1.4.0. The has_xss() function tries to block XSS attacks by matching input against regex patterns, but these patterns are incomplete and not context-aware, making them easy to bypass. An attacker can insert a malicious payload, such as a crafted anchor tag with JavaScript, into the project name field. When a user clicks this project name, the malicious script executes, loading an external script controlled by the attacker. This script steals cookies, including CSRF tokens, by sending them to the attacker's server. These stolen tokens can then be used to perform CSRF attacks against administrative users. The issue was fixed in version 1.5.0. [1]

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Impact Analysis

This vulnerability allows attackers to execute arbitrary JavaScript in the victim's browser, which can lead to redirecting users to malicious websites and stealing sensitive information such as CSRF tokens. With stolen CSRF tokens, attackers can perform Cross-Site Request Forgery attacks against administrative users, potentially compromising administrative functions and data integrity. Overall, it can lead to unauthorized actions being performed on behalf of legitimate users and exposure of sensitive session information. [1]

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Detection Guidance

This vulnerability can be detected by checking for the presence of malicious XSS payloads in user inputs, especially in the project name field on the project creation page (http://host/project/project-view/). One can monitor HTTP requests for suspicious anchor tags containing JavaScript URIs that load external scripts, such as payload.js from attacker-controlled servers. Additionally, network monitoring can be set up to detect outgoing POST requests to unusual endpoints (e.g., to port 8888) that may be exfiltrating cookies or CSRF tokens. Commands to detect such activity could include using network traffic capture tools like tcpdump or Wireshark to filter for HTTP POST requests to suspicious IPs or ports, for example: `tcpdump -i any tcp port 8888` or searching web server logs for suspicious input patterns containing 'javascript:' or external script loads. Also, scanning the Horilla version installed can be done by checking the application version to see if it is 1.4.0 or earlier, which is vulnerable. [1]

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Mitigation Strategies

The immediate mitigation step is to upgrade Horilla to version 1.5.0 or later, where the vulnerability in the has_xss() function has been fixed. Until the upgrade can be performed, restrict user input in fields such as project name to disallow JavaScript URIs or suspicious tags, and implement additional input validation and sanitization. Also, monitor and block suspicious network traffic, especially outgoing POST requests to unknown servers or ports like 8888. Limiting user privileges and educating users to avoid clicking suspicious links can reduce risk. Applying web application firewall (WAF) rules to detect and block XSS payloads may also help. [1]

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Compliance Impact

The vulnerability allows attackers to execute arbitrary JavaScript, redirect users to malicious domains, and steal CSRF tokens by exfiltrating cookies. This can lead to unauthorized access to sensitive user data and administrative functions, potentially resulting in data breaches. Such breaches could compromise compliance with data protection regulations like GDPR and HIPAA, which require safeguarding personal and sensitive information against unauthorized access and disclosure. [1]

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