CVE-2025-22497 in Simple Google Calendar Outlook Events Block Widget Plugin
Summary
by MITRE • 03/27/2025
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in A.H.C. Waasdorp Simple Google Calendar Outlook Events Block Widget allows Stored XSS.This issue affects Simple Google Calendar Outlook Events Block Widget: from n/a through 2.5.0.
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Analysis
by VulDB Data Team • 06/27/2026
This vulnerability represents a classic stored cross-site scripting flaw that undermines the security integrity of web applications by allowing malicious code execution through user-controllable input fields. The issue manifests within the A.H.C. Waasdorp Simple Google Calendar Outlook Events Block Widget, where improperly sanitized user input becomes embedded directly into web page content without adequate neutralization measures. This weakness creates an environment where attackers can inject malicious scripts that persist in the application's database and execute whenever affected pages are rendered to unsuspecting users.
The technical exploitation occurs when user-provided data containing malicious script payloads is stored within the widget's configuration or event data fields, subsequently retrieved and displayed on web pages without proper input validation or output encoding. This stored nature distinguishes it from reflected XSS vulnerabilities where the malicious payload must be delivered through external means. The vulnerability exists across all versions from the initial release through version 2.5.0, indicating a persistent flaw in the input handling mechanisms that has not been adequately addressed in the affected codebase.
From an operational perspective, this vulnerability presents significant risks to end users who may inadvertently encounter malicious scripts when viewing calendar events or widget content. Attackers can leverage this flaw to steal session cookies, perform unauthorized actions on behalf of users, redirect them to malicious sites, or even execute more sophisticated attacks such as credential harvesting or privilege escalation within the compromised application environment. The impact extends beyond simple data theft to potentially enabling full account compromise and persistent backdoor access.
The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in web applications, and follows patterns commonly associated with ATT&CK technique T1566 related to spearphishing attacks that can leverage such vulnerabilities for initial access. Organizations using this widget should immediately implement input sanitization measures including proper HTML encoding of all user-controllable data, validation of input formats, and output escaping mechanisms before rendering any content in web contexts. Additionally, implementing Content Security Policy headers and regular security audits of plugin code can significantly mitigate the risk of exploitation while maintaining application functionality.
The remediation approach should focus on comprehensive input validation and sanitization practices that ensure all user-provided data undergoes strict filtering before being stored or displayed. This includes implementing proper escaping mechanisms for HTML, JavaScript, and other contexts where user data may be rendered, along with regular security testing to identify similar vulnerabilities in related components. Updates to the widget version should be prioritized to address this flaw as versions beyond 2.5.0 are likely to contain the necessary patches and security improvements required to prevent such attacks from succeeding.