CVE-2018-20677 in Bootstrap
Summary
by MITRE
In Bootstrap before 3.4.0, XSS is possible in the affix configuration target property.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability identified as CVE-2018-20677 represents a cross-site scripting vulnerability within the Bootstrap JavaScript library affecting versions prior to 3.4.0. This issue specifically impacts the affix plugin functionality which is used to create elements that remain fixed in place during scrolling operations. The vulnerability stems from insufficient input validation and sanitization within the target property configuration of the affix plugin, creating an avenue for malicious actors to inject arbitrary JavaScript code through crafted input parameters.
The technical flaw manifests when developers configure the affix plugin with user-supplied data in the target property without proper sanitization. The affix plugin in Bootstrap is designed to make navigation elements stick to the top or bottom of the viewport during scrolling, but when the target property accepts unvalidated input, it becomes susceptible to injection attacks. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically representing a reflected XSS variant where malicious payloads are executed when the affected page loads and processes the malicious target configuration.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform session hijacking, defacement of web applications, data exfiltration, and other malicious activities. When exploited, the vulnerability allows attackers to inject malicious scripts that execute in the context of the victim's browser, potentially compromising user sessions and accessing sensitive information. The risk is particularly elevated in web applications that dynamically generate affix configurations based on user input or external data sources, making the attack surface broader than initially apparent.
Mitigation strategies for CVE-2018-20677 primarily involve upgrading to Bootstrap version 3.4.0 or later where the vulnerability has been addressed through proper input sanitization and validation. Organizations should also implement comprehensive input validation at all application layers, particularly for any user-supplied data used in JavaScript plugin configurations. The remediation process should include thorough code reviews to identify all instances where the affix plugin is used with dynamic parameters, and implementing Content Security Policy headers to provide additional defense-in-depth measures. Security teams should also consider implementing automated scanning tools that can detect vulnerable plugin configurations and ensure that all third-party libraries are regularly updated to address known vulnerabilities. This vulnerability demonstrates the critical importance of proper input validation in JavaScript libraries and the potential widespread impact when such validation is absent, aligning with ATT&CK technique T1211 for manipulating program execution flow through injection attacks.