This directive tells Squid what to do about URIs that contain whitespace characters (i.e., space and tab). The default action is to strip out the whitespace and shift the valid characters down as necessary. This is the behavior recommended by RFC 2396.
If you set this directive to
allow, Squid doesn’t change the URI. It is
passed through to the origin server as is. This setting may cause some
problems with redirectors and log file parsers. Both use whitespace as
a field delimiter, and a URI with whitespace adds an additional field
(or fields) to the redirector input line and the access.log entry.
deny setting instructs
Squid to deny such a request, as though it were blocked by the access
control rules. Note, however, that the URI is still written to
access.log with the whitespace
Squid changes whitespace characters into their RFC 1738 equivalents.
When some origin servers generate URIs that contain whitespace, this
is what they should be doing in the first place.
instructs Squid to simply cut off the URI at the first whitespace