CVE-2019-8331 identifies a cross-site scripting vulnerability in Bootstrap framework that enables XSS attacks through insufficient sanitization of the data-template attribute in tooltip and popover plugins. This vulnerability affects Bootstrap versions before 3.4.1 for the 3.x branch and before 4.3.1 for the 4.x branch, achieving a CVSS score of 6.1 (Medium severity) with an EPSS score of 84 percentile and 2.3% exploitation probability, indicating significant attack potential for web applications using vulnerable Bootstrap versions. The vulnerability details reveal that the _getContent methods in Tooltip and Popover components process user-controlled template content without proper input sanitization, allowing attackers to inject malicious JavaScript code through crafted data-template attributes that execute when tooltips or popovers are rendered. This creates substantial exploit risk for web applications utilizing Bootstrap's interactive UI components, particularly affecting websites that allow user-generated content in tooltip templates, content management systems with dynamic tooltip functionality, and applications that process external data through Bootstrap's UI enhancement features without proper input validation. The technical root cause lies in Bootstrap's Tooltip and Popover plugin implementations, where the data-template attribute processing lacks adequate input sanitization mechanisms, classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), creating a vector for known exploited vulnerabilities targeting frontend web applications. The vulnerability specifically affects the interaction between user-controlled template content and Bootstrap's rendering engine, where malicious HTML and JavaScript code embedded in data-template attributes can bypass normal content restrictions and execute in the context of the victim's browser session. With widespread adoption across JavaScript, Java, and over 18 other technologies, including 50+ affected packages spanning multiple ecosystems (RubyGems, npm, NuGet, Maven, Composer), this vulnerability demonstrates the critical importance of input sanitization in popular frontend frameworks. Mitigation strategies require upgrading to Bootstrap versions 3.4.1 or 4.3.1 and later, which implement proper sanitization for data-template attributes through built-in sanitizer functionality, or implementing immediate workarounds including strict validation of all tooltip and popover template content and avoiding user-controlled data in template attributes. Organizations should prioritize identifying all web applications using vulnerable Bootstrap versions, audit tooltip and popover implementations for user input processing, implement Content Security Policy headers to mitigate XSS impact, and maintain updated CVE database records to track similar frontend framework vulnerabilities that could compromise web application security through unsafe template processing and DOM manipulation attacks in user interface components.