The Hidden Risks of Bootstrap-Sass: Why It’s Just as Vulnerable as Bootstrap v3

Bootstrap-Sass applications may be exposed to unreported security issues due to the varying capabilities of different vulnerability scanners, which can overlook hidden risks. Some scanners rely on CVEs explicitly listing a product, or dependencies of that product, to determine if there are known vulnerabilities. Bootstrap-Sass doesn’t have any runtime dependencies and is not always listed as an affected product for CVEs. It does, however, rely directly on Bootstrap.

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A Brief History of Bootstrap-Sass

Bootstrap-Sass was created to provide developers with a way to use Bootstrap alongside the Sass preprocessor instead of Less. Initially, Bootstrap was built with Less, but many in the developer community preferred Sass due to its advanced features and improved workflow. To bridge this gap, the maintainers of Bootstrap-Sass adapted Bootstrap's stylesheets by converting them from Less to Sass while keeping the JavaScript files untouched.

For most of its lifecycle, Bootstrap-Sass was aligned with Bootstrap, offering Sass-based styling while still depending on Bootstrap’s JavaScript components. When Bootstrap v4 was released, it officially switched from Less to Sass, eliminating the need for Bootstrap-Sass as a separate project. Consequently, Bootstrap-Sass remains locked to Bootstrap v3.

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Understanding the Relationship Between Bootstrap-Sass and Bootstrap v3

Many developers or application owners assume that Bootstrap-Sass is an independent alternative to Bootstrap v3 that provides the added benefit of Sass support. However, this is a common misunderstanding. 

Bootstrap-Sass directly imports JavaScript and Less assets from Bootstrap v3 during its build process, transforming the .less files into .sass, while leaving the JavaScript unmodified.

This means that any Javascript security vulnerability present in Bootstrap v3 also exists in Bootstrap-Sass.

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Bootstrap v3: End-of-Life and Security Risks

Bootstrap v3 officially went end-of-life (EOL) on July 24, 2019. As expected, the maintainers have stopped providing security patches, leaving applications that still rely on Bootstrap v3—directly or indirectly through Bootstrap-Sass—exposed to ongoing threats.

Vulnerabilities Affecting Both Bootstrap v3 and Bootstrap-Sass

These vulnerabilities have been discovered in the latest open source version of Bootstrap v3 (v3.4.1):

• CVE-2024-6484 – A Cross-Site Scripting (XSS) vulnerability that allows malicious actors to inject scripts into web applications.
• CVE-2024-6485 – An issue related to improperly sanitized user input, leading to potential code execution risks.

Because Bootstrap-Sass inherits the JavaScript assets from Bootstrap v3, it is vulnerable to these same CVEs. If your project depends on Bootstrap-Sass, it is just as exposed as if it were running Bootstrap v3 directly.

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The Risk of Staying on Unsupported Versions

Using an unsupported version of Bootstrap-Sass means:

• No security updates – Future vulnerabilities will not be patched.
• Compliance risks – Many organizations must adhere to security policies or compliance regulations (i.e. SOC, FEDRAMP, HIPAA, PCI DSS) requiring up-to-date software applications.
• Increased attack surface – Exploits targeting Bootstrap v3 will also affect Bootstrap-Sass-based applications.

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How HeroDevs Addresses These Challenges

At HeroDevs, we specialize in keeping critical open-source software secure even after its official maintainers have ended support. Our Never-Ending Support Services for Bootstrap include:

• Ongoing security patches for newly discovered vulnerabilities.
• Backported fixes to ensure continued security without requiring a full migration.
• Proactive threat monitoring to stay ahead of emerging exploits.

If your team relies on Bootstrap v3 or Bootstrap-Sass and is concerned about security risks, HeroDevs can provide continued support and protection beyond official EOL dates.