RewriteCond %{QUERY_STRING} (\<|%3C).*script.*(\>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^s]*s)+cript.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (\<|%3C).*embed.*(\>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^e]*e)+mbed.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (\<|%3C).*object.*(\>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^o]*o)+bject.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (\<|%3C).*iframe.*(\>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^i]*i)+frame.*(>|%3E) [NC,OR] 

# Can be reduced to just this:

RewriteCond %{QUERY_STRING} (<|%3C)([^s]*s)+cript.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^e]*e)+mbed.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^o]*o)+bject.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^i]*i)+frame.*(>|%3E) [NC,OR] 

# Or if you prefer just one line, it will use the "everything atom" ".*" but only twice instead of four times as above:

RewriteCond %{QUERY_STRING} (\<|%3C).*(embed|iframe|object|script).*(\>|%3E) [NC,OR]