Executive Intelligence Brief

A critical vulnerability (CVE-2026-44977) with a CVSS score of 9 has been identified in Countly Server, a product analytics solution. This vulnerability allows a non-global application administrator to upload malicious content, which can then be executed by a global administrator, potentially leading to the exposure of sensitive authenticated session capabilities. The affected versions are prior to 24.05.50 and 25.03.44. Immediate upgrades are recommended to mitigate this critical risk.

Threat Overview

Countly Server is the server-side part of Countly, a widely used product analytics solution. The vulnerability is located in the plugins/star-rating/api/api.js and plugins/star-rating/frontend/app.js components. An attacker can exploit this vulnerability by uploading malicious content through the uploadFeedbackFile function, which is not properly validating the MIME type of uploaded files. This can lead to the storage of attacker-controlled active content. When a global administrator previews the uploaded content, the malicious payload is executed within the Countly origin, exposing sensitive authenticated session capabilities, including auth_token and csrf_token values.

Technical Deep Dive

Vulnerability Classification

This vulnerability is classified as CWE-79: Cross-Site Scripting (XSS). XSS vulnerabilities occur when an application takes user input and outputs it without proper validation or sanitization, allowing an attacker to inject malicious scripts into the application.

Root Cause Analysis

The root cause of this vulnerability is the lack of proper validation and sanitization of user-uploaded content in the Countly Server's plugins/star-rating/api/api.js and plugins/star-rating/frontend/app.js components. Specifically, the uploadFeedbackFile function does not adequately check the MIME type of uploaded files, allowing an attacker to upload malicious content. Additionally, the frontend component serves the uploaded content with an attacker-influenced Content-Type, which can lead to the execution of malicious scripts when a global administrator previews the content.

Attack Vector & Chain

The attack vector involves a non-global application administrator uploading malicious content through the uploadFeedbackFile function. The attack requires low privileges (L) and user interaction (R) from a global administrator who previews the uploaded content. The scope of the vulnerability is changed (C), as the attack can affect the confidentiality (C:H), integrity (I:H), and availability (A:H) of the system.

Exploitation Scenario Walkthrough

Scenario: Malicious Content Upload and Execution

Reconnaissance: An attacker identifies a vulnerable Countly Server instance and determines the version is prior to 24.05.50 or 25.03.44.

Weaponization: The attacker prepares a malicious payload, such as a JavaScript script, designed to exploit the XSS vulnerability.

Delivery & Exploitation: The attacker, posing as a non-global application administrator, uploads the malicious payload through the uploadFeedbackFile function. When a global administrator previews the uploaded content, the malicious script is executed within the Countly origin.

Post-Exploitation: The attacker gains access to sensitive authenticated session capabilities, including auth_token and csrf_token values, potentially allowing for further exploitation or lateral movement within the system.

Impact Realization: The attacker can use the exposed authenticated session capabilities to perform actions as a global administrator, potentially leading to data breaches, system compromise, or other malicious activities.

Exploitation in the Wild

The vulnerability is not currently being actively exploited in the wild. However, given its critical severity and the potential for exploitation, organizations using affected versions of Countly Server should prioritize immediate upgrades to versions 24.05.50 or 25.03.44.

Impact Analysis

Direct Impact

The direct impact of this vulnerability includes:

  • Execution of malicious scripts within the Countly origin
  • Exposure of sensitive authenticated session capabilities
  • Potential for data breaches or system compromise

Downstream & Cascading Effects

The downstream and cascading effects of this vulnerability may include:

  • Supply chain risk: If Countly Server is used as a component in a larger system, the vulnerability could have a broader impact
  • Regulatory implications: Depending on the nature of the data handled by Countly Server, there may be regulatory requirements for breach notification or mitigation
  • Operational disruption: Exploitation of this vulnerability could lead to system downtime or disruption of critical analytics services

Affected Products & Versions

The following versions of Countly Server are affected:

  • Prior to 24.05.50
  • Versions 25.03 to 25.03.43

The vulnerability is fixed in versions 24.05.50 and 25.03.44.

Detection & Threat Hunting

Indicators of Compromise

Indicators of compromise may include:

  • Unusual or suspicious uploads through the uploadFeedbackFile function
  • Anomalous preview activity by global administrators
  • Unexpected changes to system configurations or data

Detection Rules & Signatures

Detection rules may include:

  • Monitoring for suspicious uploads or preview activity
  • Analysis of user behavior for non-global administrators uploading content
  • Detection of malicious scripts or payloads within the system

Threat Hunting Queries

Threat hunting queries may include:

  • Searching for unusual upload activity in logs
  • Identifying global administrators who have previewed content uploaded by non-global administrators
  • Analyzing system configurations and data for signs of tampering

Remediation & Hardening

Immediate Actions (0-24 hours)

Organizations should immediately upgrade to versions 24.05.50 or 25.03.44 of Countly Server. Additionally, consider:

  • Restricting access to the uploadFeedbackFile function
  • Implementing additional validation and sanitization of user-uploaded content

Short-Term Hardening (1-7 days)

In the short term, consider:

  • Enhancing monitoring and logging for suspicious activity
  • Implementing Web Application Firewall (WAF) rules to detect and prevent exploitation
  • Conducting a thorough review of system configurations and user access controls

Strategic Recommendations

Long-term recommendations include:

  • Regularly updating and patching Countly Server instances
  • Implementing robust security controls, such as multi-factor authentication and role-based access control
  • Conducting regular security audits and penetration testing to identify and address potential vulnerabilities

Analyst Assessment

The critical severity of this vulnerability, combined with its potential impact on system security and data integrity, necessitates immediate attention from organizations using affected versions of Countly Server. While there is no evidence of active exploitation in the wild, the potential for exploitation and the ease of execution make it a high-priority risk that must be mitigated promptly.

Sources

  • National Vulnerability Database (NVD) - CVE-2026-44977