CVE-2024-38678 in Calendar.online Plugin
Summary
by MITRE • 07/20/2024
Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Calendar.Online Calendar.Online / Kalender.Digital allows Stored XSS.This issue affects Calendar.Online / Kalender.Digital: from n/a through 1.0.8.
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Analysis
by VulDB Data Team • 03/17/2025
This vulnerability represents a critical cross-site scripting flaw that enables attackers to inject malicious scripts into web pages viewed by other users. The weakness specifically manifests in the Calendar.Online and Kalender.Digital web applications where user input is not properly sanitized during the web page generation process. The vulnerability falls under CWE-79 which defines improper neutralization of input during web page generation, making it a classic stored XSS attack vector. Attackers can exploit this by submitting malicious payloads through input fields that are then stored on the server and executed whenever other users view the affected pages.
The technical implementation of this vulnerability occurs when user-supplied data flows through the application's input validation mechanisms without adequate sanitization or encoding. When the calendar application generates web pages containing this unsanitized user input, the browser interprets the malicious script code as part of the legitimate page content rather than as executable instructions. This allows attackers to execute arbitrary JavaScript in the context of other users' browsers, potentially leading to session hijacking, credential theft, or further exploitation of the victim's browser environment. The vulnerability affects all versions from the initial release through version 1.0.8, indicating this flaw has persisted for some time without proper remediation.
The operational impact of this stored XSS vulnerability is severe and multifaceted. An attacker who successfully exploits this vulnerability can gain persistent access to users' sessions, potentially allowing them to perform actions on behalf of victims with their privileges. This includes accessing sensitive calendar data, modifying events, or even gaining administrative access if the victim has elevated permissions. The stored nature of the vulnerability means that once an attacker successfully injects malicious code, it remains active until manually removed from the application's database, providing extended attack windows. Additionally, the vulnerability could be leveraged to redirect users to malicious domains, harvest cookies, or perform phishing attacks against authenticated users.
Organizations should implement immediate mitigations including comprehensive input validation and output encoding for all user-supplied data. The application should employ proper HTML encoding for any data that is rendered in web pages, ensuring that special characters are properly escaped before display. Implementing Content Security Policy headers can provide additional protection against script execution, while regular security scanning and code reviews should be conducted to identify similar vulnerabilities. The vulnerability aligns with ATT&CK technique T1566.001 which covers spearphishing with malicious attachments, as attackers may use this vulnerability to deliver malicious payloads to unsuspecting users. Organizations should also consider implementing web application firewalls and monitoring for suspicious input patterns to detect potential exploitation attempts. The remediation process must include thorough testing to ensure that all input fields are properly sanitized and that output encoding is consistently applied throughout the application's web page generation logic.