CVE-2026-24778: Ghost CMS XSS Vulnerability

CVE-2026-24778 Overview

Ghost is an open source content management system that has been identified as vulnerable to a Cross-Site Scripting (XSS) attack. In Ghost versions 5.43.0 through 5.12.04 and 6.0.0 through 6.14.0, an attacker can craft a malicious link that, when accessed by an authenticated staff user or member, would execute JavaScript with the victim's permissions, potentially leading to account takeover. The vulnerability specifically affects the Ghost Portal component, which is the members-facing interface for authentication and membership management.

Critical Impact

Successful exploitation allows arbitrary JavaScript execution in the context of authenticated users, potentially enabling full account takeover of staff members and administrators.

Affected Products

• Ghost CMS versions 5.43.0 through 5.121.0
• Ghost CMS versions 6.0.0 through 6.14.0
• Ghost Portal versions 2.29.1 through 2.51.4 and 2.52.0 through 2.57.0

Discovery Timeline

• 2026-01-27 - CVE-2026-24778 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-24778

Vulnerability Analysis

This vulnerability is classified as Cross-Site Scripting (CWE-79), a web application vulnerability that occurs when untrusted data is included in a web page without proper validation or escaping. In the case of Ghost CMS, the Portal component failed to properly sanitize user-supplied input within maliciously crafted URLs.

The attack requires user interaction, specifically requiring an authenticated staff user or member to click on a malicious link. Once clicked, the injected JavaScript executes within the security context of the victim's browser session, inheriting all permissions and access rights of the authenticated user. For staff users with administrative privileges, this could lead to complete compromise of the Ghost installation.

Ghost Portal automatically loads via CDN for most installations, which means the vulnerability affects a broad range of deployments unless organizations have implemented custom or self-hosted Portal versions.

Root Cause

The root cause of CVE-2026-24778 lies in insufficient input validation and output encoding within the Ghost Portal component. The application failed to properly sanitize URL parameters before reflecting them in the rendered page content, allowing an attacker to inject executable script content through specially crafted links.

This type of reflected XSS vulnerability typically occurs when dynamic content is generated from user input without adequate security controls such as input validation, output encoding, or Content Security Policy (CSP) headers.

Attack Vector

The attack is network-based and requires minimal attacker privileges to execute. An adversary would craft a malicious URL containing JavaScript payload and distribute it through phishing emails, social media, or other communication channels targeting Ghost CMS users. When a victim clicks the link while authenticated to the Ghost admin panel or members area, the malicious script executes with their session privileges.

The exploitation chain typically follows this pattern: the attacker identifies a vulnerable Ghost installation, crafts a URL with embedded JavaScript, delivers it to target users through social engineering, and upon click, the script can steal session cookies, modify content, create admin accounts, or perform other privileged actions on behalf of the victim.

For detailed technical information about the vulnerability mechanism and the specific fix, refer to the GitHub Security Advisory GHSA-gv6q-2m97-882h and the related commit.

Detection Methods for CVE-2026-24778

Indicators of Compromise

• Unusual outbound requests from the Ghost Portal component to external domains
• JavaScript execution errors in browser console logs from legitimate users accessing suspicious links
• Session tokens being sent to unauthorized external endpoints
• Unexpected administrative actions or account modifications without corresponding user activity
• Web server logs containing URLs with encoded script tags or JavaScript event handlers targeting Portal endpoints

Detection Strategies

• Monitor web application firewall (WAF) logs for requests containing XSS patterns such as <script>, javascript:, onerror=, or encoded variants targeting Ghost Portal
• Implement Content Security Policy (CSP) reporting to detect inline script execution attempts
• Deploy browser-based XSS detection tools that can identify reflected script injection in real-time
• Review Ghost application logs for anomalous authentication patterns following suspicious URL accesses

Monitoring Recommendations

• Enable detailed logging for all Ghost Portal authentication and member activity
• Configure alerting for multiple failed authentication attempts followed by successful logins from different IP addresses
• Monitor for changes to administrative user accounts, particularly new admin account creation
• Implement real-time alerting on CSP violation reports that indicate script injection attempts

How to Mitigate CVE-2026-24778

Immediate Actions Required

• Upgrade Ghost 5.x installations to version 5.121.0 or later immediately
• Upgrade Ghost 6.x installations to version 6.15.0 or later immediately
• For custom or self-hosted Portal deployments, manually rebuild from or update to Portal version 2.51.5 (for Ghost 5.x) or 2.57.1 (for Ghost 6.x)
• Educate staff users about the risks of clicking unknown or suspicious links while authenticated to Ghost

Patch Information

Ghost has released patched versions that address this XSS vulnerability. For Ghost 5.x users, version 5.121.0 loads Portal v2.51.5 which contains the security fix. For Ghost 6.x users, version 6.15.0 loads Portal v2.57.1 with the patch applied.

Since Ghost automatically loads the latest patch of the Portal component via CDN for standard installations, most deployments will receive the fix automatically upon upgrading to the patched Ghost version. Organizations using customized or self-hosted Portal versions must manually update to ensure protection.

The fix can be reviewed in the GitHub commit da858e640e88e69c1773a7b7ecdc2008fa143849.

Workarounds

• Implement a Web Application Firewall (WAF) with rules to block common XSS payloads targeting Ghost endpoints
• Configure strict Content Security Policy headers to prevent inline script execution
• Restrict staff user access to trusted networks or VPN-only connections
• Enable multi-factor authentication for all administrative accounts to reduce account takeover impact

# Example: Add Content Security Policy headers in nginx configuration
# Add to your Ghost nginx server block
add_header Content-Security-Policy "default-src 'self'; script-src 'self' https://unpkg.com; frame-ancestors 'none';" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-XSS-Protection "1; mode=block" always;