Hey there,
we’ve a integration within our website where we send submitted forms to AC via the v1 API.
This works well and still works (somehow) but there is a general issue since 2-3 weeks.
We do submit the request to create a contact (or to update it) via the:
https://<account>.api-us1.com/admin/api.php?api_action=contact_add&api_output=json&api_key=<key>
This hasn’t changed and worked well for us since years.
Two weeks ago we introduced a new form to the website which uses the same API and just accepts the email as an input as many of our forms, nothing odd here. But when submitting the form on the website the API responses with a 500 Error:
Unknown Error",“message”:"An unknown error has occurred while processing the request (Reason: com.fasterxml.jackson.core.JsonParseException: Unexpected character (‘<’ (code 60)): expected a valid value (number, String, array, object, ‘true’, ‘false’ or ‘null’)\n at [Source: (org.apache.http.conn.EofSensorInputStream); line: 1, column: 2]). Please contact your administrator.
The contact is still created in Active Campaign and the form is submitted perfectly, but the API responses with this error. After some research we’ve figured that the API of AC is responding with the XML format instead of the requested JSON format.
My assumption now is that this is a bug in the API itself - or has anything changed with new created forms? Since old form (which have been created years ago) are still working without this error.
Currently our frontend in the website obv. outputs an error to the user while actually everything worked…
Happy to get any tip, answer or comment 
Thanks in advance - if you need any further details - let me know.
Cheers,
Steffen
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