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I was trying to learn how object.prototype function in javascript then I came across this snippet of code .which I don't understand?
// Poisoning Object.prototype
Object.prototype.bar = 1;
var foo = {goo: undefined};
foo.bar; // 1
'bar' in foo; // true
foo.hasOwnProperty('bar'); // false
foo.hasOwnProperty('goo'); // true
foo has the property bar which is defined in the line number 3 and having the value of undefined .Please guide then why foo.hasOwnProperty('bar') returns false in this case
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Prototype Pollution is a vulnerability that allows attackers to exploit the rules of the JavaScript programming language, by injecting properties into existing JavaScript language construct prototypes, such as Objects to compromise applications in various ways. JavaScript allows all Object attributes to be altered.
A prototype pollution exploitation starts when threat actors inject a payload into an input, like a URL, that builds the client-side logic or application rendering. For example, a URL parser can assign JavaScript objects properties without verifying if the target property is linked correctly to the Object prototype.
Freeze the Object.prototype freeze() method could freeze an object so that the object is no longer able to be modified.
Collect 5 cm3 of blood in a plain (red top) vacutainer. Centrifuge at 3000 r.p.m. for 10 min. Use a 5 cm3 syringe and separate serum, and inject 2.5 ml of the serum deep intramuscularly into the gluteus muscle with a 22 no needle. Repeat the procedure for 8 weeks; later, fortnightly injections are advised.
All objects in JavaScript are descended from Object. all objects inherit methods and properties from Object.prototype.
In your example when you try to get the foo.bar, it doesn't find bar in the foo, so it is going to the prototype of the foo and tries to find it there.
hasOwnProperty - only checks a property which is exactly in the your foo.
Here is what your foo looks like
For deep understanding you can read this chapter.
You Don't Know JS
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