GHSA-963h-3v39-3pqf Vega vulnerable to Cross-site Scripting via RegExp.prototype[@@replace]

• npm vega: < 5.32.0 → fixed in 5.32.0 • npm vega-functions: < 5.17.0 → fixed in 5.17.0

Impact Users running Vega/Vega-lite JSON definitions could run unexpected JavaScript code when drawing graphs, unless the library is used with the `vega-interpreter`. Workarounds • Use `vega` with expression interpreter • Upgrade to a newer Vega version (`5.32.0`) POC Summary Calling `replace` with a `RegExp`-like pattern calls `RegExp.prototype[@@replace]`, which can then call an attacker-controlled `exec` function. POC Details Consider the function call `replace('foo', {__proto__: /h/.constructor.prototype, global: false})`. Since `pattern` has `RegExp.prototype[@@replace]`, `pattern.exec('foo')` winds up being called. The resulting malicious call looks like this: ``` replace(, {__proto__: /h/.constructor.prototype, exec: , global: false}) ``` Since functions cannot be returned from this, an attacker that wishes to escalate to XSS must abuse `event.view` to gain access to `eval`. Reproduction steps ``` {"$schema":"https://vega.github.io/schema/vega/v5.json","signals":[{"name":"a","on":[{"events":"body:mousemove{99999}","update":"replace('alert(1)',{__proto__:/h/.constructor.prototype,exec:event.view.eval,global:false})"}]}]} ```