The web application is unable to accept any more connections because of network socket exhaustion: A Denial of Service (DoS) attack often floods the web server with an overwhelming number of requests, leading to network socket exhaustion. This can prevent the server from accepting new legitimate connections, effectively disrupting service.

The web application server is unable to accept new client sessions due to memory exhaustion: DoS attacks can consume a significant amount of server memory, causing memory exhaustion. This results in the web application being unable to accept new client sessions or handle requests properly.

Cross-Site Scripting (XSS) is a type of web security vulnerability that allows attackers to inject malicious scripts into web pages viewed by users. This can lead to session hijacking, credential theft, or redirection to malicious sites. XSS attacks typically exploit vulnerabilities in web applications that fail to properly sanitize user input.

Here's an analysis of the given options:

A . SELECT username FROM accounts WHERE username='admin';-- ' AND password='password';

This is an example of SQL Injection (SQLi) rather than XSS. It manipulates SQL queries to bypass authentication, not execute JavaScript in a user's browser.

B .

This is a classic XSS attack.

It uses an tag with a non-existent src attribute.

The onerror event triggers when the image fails to load, executing alert(document.cookie);, which can expose session cookies.

This method is commonly used for stealing cookies or executing arbitrary scripts.

C . SELECT username FROM accounts WHERE username='XSS' ' AND password='alert('http://badurl.com')';

This is neither a valid SQL injection nor a valid XSS attack.

The syntax suggests an incorrect SQL query rather than JavaScript execution in a browser.

D . <IMG SRC='xss.png'>

This is not a valid XSS attack unless there is an additional event handler like onload, onerror, or onmouseover executing JavaScript.

By itself, it just loads an image and does not execute any malicious script.

Thus, Option B is the correct answer as it represents a real-world XSS attack technique.

OWASP XSS Guide: https://owasp.org/www-community/attacks/xss/

Fortinet XSS Protection Documentation: https://docs.fortinet.com/

Virtual proxy: In virtual proxy mode, FortiWeb acts as an intermediary between clients and the server, and it can modify HTTP packets. It performs various security checks, such as inspecting and filtering HTTP traffic before forwarding it to the web server.

Reverse proxy: In reverse proxy mode, FortiWeb sits between the client and the server, handling incoming requests from clients, modifying or inspecting HTTP packets as needed, and forwarding them to the backend servers.

Making a secondary HTTPS connection to a server where FortiWeb acts as a client: When FortiWeb needs to connect to an external server via HTTPS (acting as a client), it may use its own certificates for that connection.

An administrator session connecting to the GUI using HTTPS: FortiWeb uses its own certificates to secure the HTTPS connection between the administrator and the FortiWeb GUI. This ensures secure access for management purposes.

If a client has been incorrectly blocked due to a period block, the FortiWeb administrator can manually release the IP address from the blocklist. This allows the client to access the application again before the block expires naturally.