What is the biggest threat to Web 2.0 technologies?

Hackers today have anever-increasinglist of weaknesses in the web application structure at
their disposal, which they can exploit to accomplish a wide variety of malicious tasks.

New flaws in web application security measures are constantly being researched, both by
hackers and by security professionals. Most of these flaws affect all dynamic web
applications whilst others are dependent on specific application technologies. In both cases,
one may observe how the evolution and refinement of web technologies also brings about
new exploits which compromise sensitive databases, provide access to theoretically secure
networks, and pose a threat to the daily operation of online businesses.
What is the biggest threat to Web 2.0 technologies?

A.
SQL Injection Attacks

B.
Service Level Configuration Attacks

C.
Inside Attacks

D.
URL Tampering Attacks