XSS scripting assertion on REST PATCH request via GET method

Ok,

simple example

The PATCH operation is used on a resource that is "Phones"
The json body has a unique Id (int), the phone number (string) and a comment (string)

I set the XSS security test to execute PATCH requests in order to update the phone with id = 5 and target both strings in the body of the following request

{
"PhoneUniqueId": 5,
"PhoneNumber": "123123123" ,
"PhoneComment": "this is a comment"
}

As SoapUI iterates through its list of XSS strings and replacing the target fields it issues the following in sequence:

{
"PhoneUniqueId": 5,
"PhoneNumber": "<PLAINTEXT>" ,
"PhoneComment": "this is a comment"
}

{
"PhoneUniqueId": 5,
"PhoneNumber": "<SCRIPT>alert(1)</SCRIPT>" ,
"PhoneComment": "this is a comment"
}

...

{
"PhoneUniqueId": 5,
"PhoneNumber": "123123123" ,
"PhoneComment": "<PLAINTEXT>"
}

{
"PhoneUniqueId": 5,
"PhoneNumber": "123123123" ,
"PhoneComment": "<SCRIPT>alert(1)</SCRIPT>"
}

For the reasons I have mentioned already the existing XSS assertion setup is not helpful. So unless I'm missing something with the XSS assertion config, have to opt for a Custom Script Assertion.

The idea is this:

1. Get the PhoneUniqueId from the PATCH request and the field that was used, let's say it was PhoneComment
2. Issue a GET for the same PhoneUniqueId 
3. Check the GET response body and see if the PhoneComment value has an XSS string

Checking through internet I came up with something very rough like this:

def testCase = messageExchange.modelItem.testCase
def ResponseMessage = testCase.testSteps["GET_Phones"].testRequest.response.contentAsString

File file1 = new File("C:/XSS_Vectors")
List textLine = file1.readLines()
try{
textLine.each{
if (ResponseMessage.contains(it)){
log.info 'XSS_Vector: ' + it +' was found in message'
res = false
throw new Exception('XSS_Vector: ' + it +' was found in message')
}
}
assert res
} catch(Exception e) {
log.error("Exception: ${e}")
assert res
}

The XSS_Vectors file has the strings used by SoapUI and GET_Phones is a testcase that performs the GET operation on the "PhoneUniqueId": 5 (hardcoded value)

Two problems with that: 
1. I do not know which field was used in the PATCH request so as to target the proper field only in my check. Let's say that the 2nd PATCH request from above goes through and the XSS string is stored as is. When I run the custom script for the 3rd and 4th one I will always get an indication even if "PhoneComment" was treated correctly, simply because the GET response will always have "PhoneNumber": "<SCRIPT>alert(1)</SCRIPT>"

2. I want to be able to use a similar approach for POST on the same resource that is used for inserting new entries. The body is the same as PATCH. The difference is that with POST I have to provide a unique PhoneUniqueId, something like this random generation

{
"PhoneUniqueId": "${=(new java.util.Random()).nextInt(10000000)}",
"PhoneNumber": "69${=(new java.util.Random()).nextInt(10000000).toString()}" ,
"PhoneComment": "<SCRIPT>alert(1)</SCRIPT>"
}

As a result I cannot have a GET request to be used with a hardcoded "PhoneUniqueId" either

hope this helps

Nikos