GHSA-mp7w-mhcv-673j

Vega allows Cross-site Scripting via the vlSelectionTuples function

### Summary The `vlSelectionTuples` function can be used to call JavaScript functions, leading to XSS. ### Details [`vlSelectionTuples`](https://github.com/vega/vega/blob/b45cf431cd6c0d0c0e1567f087f9b3b55bc236fa/packages/vega-selections/src/selectionTuples.js#L14) calls multiple functions that can be controlled by an attacker, including one call with an attacker-controlled argument. Example call: `vlSelectionTuples([{datum:<argument>}], {fields:[{getter:<function>}]})` This can be used to call `Function()` with arbitrary JavaScript and the resulting function can be called with `vlSelectionTuples` or using a type coercion to call `toString` or `valueOf`. ### PoC ``` {"$schema":"https://vega.github.io/schema/vega/v5.json","signals":[{"name":"a","init":"+{valueOf:vlSelectionTuples([{datum:'alert(1)'}],{fields:[{getter:[].at.constructor}]})[0].values[0]}"}]} ```