You have forgotten your password of an online shop. The web application of that online shop asks you to enter your email so that they can send you a new password. You enter your email [email protected]…

When a user enters special characters such as single quotes, angle brackets, or percent signs into an email field, the server-side code may fail to sanitize or escape them properly, causing the backend processing or database query to throw an exception. This results in a visible server error rather than a graceful validation message, and is indicative of inadequate input validation on the application. This is also the basis of SQL injection vulnerabilities where a single quote in input breaks a query string.

An invalid email format would typically be caught by client-side or server-side validation and return a user-friendly validation message, not a server error.

If the remote server were down, the browser would display a connection timeout or 502/503 HTTP error before the web application could even display a server error message.

A slow internet connection would cause delayed responses or timeouts, not a server-side application error returned by the web application itself.