Cookie injection leads to complete DoS over whole domain *.mackeeper.com. Injection point accountstage.mackeeper.com/

How it was found

Summary:

The cookie bomb works by setting large cookies that are way too big making the server decline any request send with them for having a too long request header.

PoC

1. Open below link and click on link https://unequaledfloor.htmlpasta.com/

2. Now open https://accountstage.mackeeper.com/ or https://.mackeeper.com/ , these domains won't open anymore.

Impact

The escape function is used, which means a value consisting of special symbols will become three times longer. For example ,,, will turn into %2C. That means an attacker can create a valid link of proper length accepted both by the browser and the server, which however will make the cookie too long.