Malformed JSON data and Character encoding

Hi team,

The following POST request triggers the violation "Malformed JSON data" .

POST https://10.10.1.80/ HTTP/1.1
Content-Type: application/json; charset=iso-8859-1
Host: 10.10.1.80
Expect: 100-continue
Connection: Keep-Alive
Content-Length: 81
 
{
    "firstname":"John",
    "lastname":"Doe",
    "terminal":"12345"
}

The learning suggestion for this violation is to remove the JSON profile and "apply value and content signatures" to the URL which is not something I want to do.

After some troubleshooting, I noticed that :

• If I remove the "é" character from the posted data then the violation is not triggered.
•  
• If I remove the ";charset= iso-8859-1" from the Content-Type header the violation is not triggered as well.
•  

I would like to understand why the charset needs to be at its default value (utf-8) for the bigip to understand the "é" character.

PS: I'm in LAB environment and in version 13.1.0.3.

Many thanks,

Karim BENYELLOUL