Security: Theme selection via DOM input without validation#629
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offa merged 1 commit intooffa:masterfrom Apr 7, 2026
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The `changeCSS` function constructs a URL by interpolating user-controlled input (`theme` parameter from the `<select>` element) directly into a CDN URL template. While the current `<select>` restricts values, if the function were called programmatically (e.g., via browser console or if the DOM is manipulated), an attacker could inject an arbitrary path into the stylesheet URL, potentially loading a malicious CSS file from the CDN. Affected files: index.html Signed-off-by: Trần Bách <45133811+barttran2k@users.noreply.github.com>
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Problem
The
changeCSSfunction constructs a URL by interpolating user-controlled input (themeparameter from the<select>element) directly into a CDN URL template. While the current<select>restricts values, if the function were called programmatically (e.g., via browser console or if the DOM is manipulated), an attacker could inject an arbitrary path into the stylesheet URL, potentially loading a malicious CSS file from the CDN.Severity:
lowFile:
index.htmlSolution
Validate the
themeparameter against an allowlist of known themes before constructing the URL:const allowedThemes = ['darkly', 'united', 'flatly', 'quartz']; if (!allowedThemes.includes(theme)) return;Changes
index.html(modified)Testing