Watchguard Firebox X1000 Reference Manual page 206

CHAPTER 10: Field Definitions
Firebox and performs caching of Web data. It is not supplied by
WatchGuard.
Safe Content tab
194
IP
Enter the IP address of the HTTP caching proxy.
Port
Enter the port number of the HTTP caching proxy.
Allow only safe content types
Enable this checkbox to permit only the content types listed in the
box below. This arrangement allows you to easily block
everything and allow in only those MIME types you deem
acceptable security risks. For a list of content types, see Chapter 2
in the Reference Guide.
Allowed Content Types list
With the Allow only safe content types checkbox enabled, only
those content types listed here will pass through the HTTP proxy.
Add
Click to add a new entry to the list above.
Remove
Click an entry from the list above and click to remove it.
Deny unsafe path patterns
Select to deny unsafe path patterns.
Unsafe Path Patterns list
With the Deny unsafe path patterns checkbox enabled, the path
patterns listed here will be denied.
Add
Click to add a new entry to the unsafe path patterns list.
Remove
Click to remove the selected item from the list above.
WatchGuard Firebox System