CVE-2026-85599 in Grav
Summary
by MITRE • 09/04/2026
Grav Shortcode Core before 6.2.5 contains stored cross-site scripting vulnerabilities in the [lorem] tag parameter and [details] summary parameter that are written to rendered pages without escaping. Attackers with page-edit access can inject arbitrary HTML and JavaScript that executes in the browsers of all page visitors, including administrators.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in Grav Shortcode Core prior to version 6.2.5 represents a critical security flaw rooted in insufficient input validation and output encoding mechanisms within specific shortcode implementations. Specifically, the [lorem] tag parameter and the [details] summary parameter fail to properly sanitize user-supplied data before it is rendered into HTML pages. This architectural oversight allows for stored cross-site scripting attacks where malicious scripts are persistently saved on the target server rather than being executed transiently through a crafted link. The core technical failure lies in the absence of robust escaping routines that would neutralize special characters such as angle brackets, quotes, and ampersands when these parameters are processed by the rendering engine. Consequently, any content injected via these shortcodes is interpreted directly by web browsers as executable code rather than plain text data.
The operational impact of this vulnerability is severe due to its stored nature combined with broad user accessibility requirements. Unlike reflected cross-site scripting which typically requires tricking a specific victim into clicking a malicious link, stored vulnerabilities persist on the server and are served to every visitor who accesses the affected page. This means that an attacker only needs access to edit pages within the Grav CMS environment to deploy the payload once, after which it will execute in the browsers of all subsequent visitors. The requirement for page-edit access is relatively low compared to administrative privileges, making this vulnerability particularly dangerous as it can be exploited by content editors or contributors who may not have full system control but possess sufficient trust and permissions within the application interface.
From a threat modeling perspective, this flaw aligns with CWE-79 Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting XSS. The attack vector is classified under ATT&CK technique T1059 Command and Scripting Interpreter specifically JavaScript execution via browser-based interactions. Once the malicious script executes in a victim's browser, it operates within the context of the Grav CMS domain. This allows attackers to perform session hijacking by stealing authentication cookies or tokens, conduct keylogging to capture sensitive information entered on the page, deface websites by altering DOM elements, or redirect users to phishing sites designed to steal credentials for other services where the user is authenticated via single sign-on mechanisms.
Mitigation strategies must focus primarily on upgrading the Grav Shortcode Core plugin to version 6.2.5 or later which addresses these sanitization gaps through improved encoding practices. For organizations unable to immediately patch, temporary mitigations include restricting page-editing permissions to only highly trusted individuals and implementing a Content Security Policy that restricts script execution from untrusted sources although this is less effective against stored XSS within the same origin. Additionally, deploying Web Application Firewalls with rules specifically tuned for detecting encoded or obfuscated JavaScript payloads in form submissions can provide an additional layer of defense by blocking requests containing suspicious patterns associated with cross-site scripting attempts before they reach the application logic.