CVE-2018-20676 in Bootstrap
Summary
by MITRE
In Bootstrap before 3.4.0, XSS is possible in the tooltip data-viewport attribute.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability identified as CVE-2018-20676 represents a cross-site scripting weakness in the popular web framework Bootstrap prior to version 3.4.0. This security flaw specifically affects the tooltip functionality and occurs within the data-viewport attribute handling mechanism. The issue arises when developers utilize Bootstrap's tooltip component with user-provided data in the viewport attribute, creating an avenue for malicious actors to inject harmful scripts into web applications. The vulnerability is particularly concerning because Bootstrap is widely adopted across numerous web platforms and applications, amplifying the potential impact of exploitation.
The technical root cause of this vulnerability lies in insufficient input validation and sanitization within Bootstrap's tooltip implementation. When the data-viewport attribute is processed, the framework fails to properly escape or validate user-supplied content, allowing arbitrary HTML or JavaScript code to be executed within the context of the web application. This occurs because the tooltip component directly incorporates the viewport attribute value into the DOM without adequate sanitization measures. The vulnerability is classified as a classic XSS attack vector, specifically falling under CWE-79 - Improper Neutralization of Input During Web Page Generation, where user-controllable data is improperly handled during HTML generation. The flaw demonstrates poor secure coding practices and inadequate defense-in-depth measures within the framework's security architecture.
The operational impact of CVE-2018-20676 extends beyond simple script execution, as it can enable attackers to perform session hijacking, deface web applications, steal sensitive user data, or redirect victims to malicious websites. When exploited, this vulnerability allows attackers to inject malicious scripts that can access cookies, local storage, and other sensitive information stored in the browser. The attack surface is particularly wide given Bootstrap's extensive usage across enterprise applications, government portals, and consumer-facing websites. Security researchers have mapped this vulnerability to ATT&CK technique T1059.001 - Command and Scripting Interpreter: PowerShell, as the injected scripts can leverage various command execution capabilities. The vulnerability can be exploited through multiple vectors including direct user input, manipulated URL parameters, or even through compromised third-party components that utilize Bootstrap.
Mitigation strategies for this vulnerability require immediate action including upgrading to Bootstrap version 3.4.0 or later where the issue has been resolved through proper input sanitization and validation. Organizations should also implement comprehensive input validation at multiple layers of their application architecture, including client-side and server-side filtering of user-provided data. The remediation process should involve thorough code reviews to identify any custom implementations that might be vulnerable, as well as implementing Content Security Policy headers to limit script execution. Security teams should conduct vulnerability assessments across their entire application portfolio to identify other potential XSS vulnerabilities in similar components. Additionally, developers should be trained on secure coding practices and the importance of proper input sanitization, particularly when working with frameworks that handle user data through attributes like data-viewport. The fix implemented by Bootstrap developers involved strengthening the attribute validation mechanism and ensuring that all user-supplied content is properly escaped before being incorporated into the DOM structure, aligning with industry best practices for preventing XSS vulnerabilities.