Error Page Content Spoofing or Text Injection

Target: https://gopher.hey.com/ Description: Content spoofing, also referred to as content injection, "arbitrary text injection" or virtual defacement, is an attack targeting a user made possible by an injection vulnerability in a web application. When an application does not properly handle user-supplied data, an attacker can supply content to a web application, typically via a parameter value, that is reflected back to the user. This presents the user with a modified page under the context of the trusted domain. Steps to Reproduce: 1. Go to https://gopher.hey.com/ 2. Type any thing after slash, it will be reflected on the page. Reference: https://hackerone.com/reports/498562 https://hackerone.com/reports/327671 ## Impact This attack is typically used as, or in conjunction with, social engineering because the attack is exploiting a code-based vulnerability and a user's trust. As a side note, this attack is widely misunderstood as a kind of bug that brings no impact.