What makes web application vulnerabilities so aggravating?

What makes web application vulnerabilities so aggravating? (Choose two)

A.
They can be launched through an authorized port.

B.
A firewall will not stop them.

C.
They exist only on the Linux platform.

D.
They are detectable by most leading antivirus software.

Explanation:
As the vulnerabilities exists on a web server,incoming traffic on port 80 will probably
be allowed and no firewall rules will stop the attack.