What sort of security breach is this policy attempting to mitigate?

A company’s security policy states that all Web browsers must automatically delete their HTTP browser cookies upon terminating.

What sort of security breach is this policy attempting to mitigate?
A . Attempts by attackers to access the user and password information stored in the company’s SQL database.
B . Attempts by attackers to access Web sites that trust the Web browser user by stealing the user’s authentication credentials.
C . Attempts by attackers to access password stored on the user’s computer without the user’s knowledge.
D . Attempts by attackers to determine the user’s Web browser usage patterns, including when sites were visited and for how long.

Answer: B