Avoid mutable default parameter.

monkey/infection_monkey/exploit/shellshock.py

@@ -172,10 +172,13 @@ class ShellShockExploiter(HostExploiter):
             LOG.info("File %s exists on remote host" % file_path)
         return resp
 
-    def attempt_exploit(self, url, attacks=_attacks):
+    def attempt_exploit(self, url, attacks=None):
         # Flag used to identify whether the exploit has successfully caused the
         # server to return a useful response
 
+        if not attacks:
+            attacks = self._attacks
+
         LOG.debug("Attack Flag is: %s" % self.success_flag)
 
         LOG.debug("Trying exploit for %s" % url)