Steps to reproduce:

1. Send test alert using the SIGNL4 media type
2. The JSON payload is not correct

Result:

Right now there is no issue because SIGNL4 can cope with the wrong format.

I recommend fixing it to use the correct format to make sure future versions will still work.

Expected:
The fix applies to this file:

https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/templates/media/signl4/media_signl4.yaml

Line 114 should be changed from:

response = request.post(endpoint, 'payload=' + payload);

to:

response = request.post(endpoint, payload);

Attached please find the complete adapted file.