github / github/codeql

False positive for Prototype-polluting function

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#18,327 4 comentarios 1 reacción 0 asignados Ver en GitHub
false-positive javascript
Lenguaje dominante
CodeQL
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2 d 15 h
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Descripción

I check for prototype polluting property keys in a set of reserved keys which include `__proto__` and `constructor`.

This shouldn't even be necessary since the key, value come from Object.entries which according to MDN will only iterate own enumerable string-keyd property. ie. never `__proto__` or `constructor`.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries

![image](https://github.com/user-attachments/assets/55d3c365-db31-4132-b528-b147cddb6043)

Still the lookup in the set does not work.

```js
// Iterate through the source own enumerable string-keyed property key-value pairs.
for (const [key, value] of Object.entries(source)) {

// This for codeql only. key, value of Object.entries should ensure that only own properties are parsed
if (!source.hasOwnProperty(key)) continue;

// The ignoreKeys contain checks against prototype pollution.
if (new Set(['__proto__', 'constructor', 'mapview']).has(key)) {

continue;
}
```

CodeQL looks at the right place but ignores the check for the set.

https://github.com/GEOLYTIX/xyz/security/code-scanning/217

![image](https://github.com/user-attachments/assets/d1cfd2a3-fde5-439e-b3b2-cc82ae87694e)

The only way I can make the issue go away is by doing a === check on the string value like so.

```js
// Prevent prototype polluting assignment.
if (key === '__proto__' || key === 'constructor') return true;
```

Even though I know that this issue can not happen I need to add this extra line to make the CodeQL warning go away.

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