Vulnerabilities — Bootstrap V4.0.0-alpha.6

Bootstrap has long been the world's most popular front-end component library. However, using older, pre-release versions like v4.0.0-alpha.6 (released in January 2017) comes with significant security risks that many developers overlook. In this post, we'll examine the known vulnerabilities affecting this specific alpha release and why you should upgrade immediately. Bootstrap v4.0.0-alpha.6 was an important milestone in the Bootstrap 4 development cycle, introducing significant changes from the alpha.5 release. However, as an alpha version , it was never intended for production use. It lacked many security hardening measures that would later be implemented in the stable v4.0.0 release (January 2018) and subsequent versions. Known Vulnerabilities in v4.0.0-alpha.6 While the Bootstrap team maintains good security practices, several vulnerabilities have been documented that affect this specific alpha release: 1. Cross-Site Scripting (XSS) via Data Attributes (CVE-2019-8331) Severity: Medium Affected components: Tooltip, Popover

If you're maintaining a legacy project still running alpha.6, treat it as a critical security debt that needs immediate remediation. Modern browsers, security standards, and attack techniques have evolved significantly since 2017 — don't let your front-end security remain in the past. Have questions about migrating from Bootstrap alpha versions? Drop a comment below or reach out on Twitter @yourhandle. Stay secure!

Published: April 17, 2026

The tooltip and popover plugins in Bootstrap versions prior to 3.4.1 and 4.3.x before 4.3.1 contained an XSS vulnerability. While alpha.6 predates these fixes, the vulnerable code pattern exists in this alpha release. Attackers could inject malicious JavaScript through custom data-* attributes when the tooltip or popover was initialized with unsanitized user input.

// Vulnerable example in alpha.6 // An attacker could inject: data-trigger="click" data-html="true" data-content="<img src=x onerror=alert(1)>" $('#element').tooltip(); Severity: Low to Medium Affected components: Tooltip, Popover

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