Tracking script inserts field id instead of value in extended fields if fingerprint tracking is enabled

[zero-one-devteam]

What type of report is this:

Q	A
Bug report?	possible bug
Feature request?
Enhancement?

Description:

I‘ve upgraded to 2.15.1 and I am using extended fields. Inserting and updating values work perfect via api. But when using the mtc.js tracking script, every pageview inserts a number in each extend field (like 23, 24). This only happens with extended fields not with contact fields.

If a bug:

Q	A
Mautic version	2.15.1
PHP version

Steps to reproduce:

1. activate extended field plugin
2. using tracking script on the website mtc.js
3. Mautic inserts numbers in each extended field

Log errors:

Please check for related errors in the latest log file in [mautic root]/app/log/ and/or the web server's logs and post them here. Be sure to remove sensitive information if applicable.

[zero-one-devteam]

It's not caused by Mautic 2.15.1. I deployed 2.15.0 on a staging system (same infrastructure on AWS, only separate EB App), the error is the same. If a contact is created, a number is inserted in each extended field. It is enumerated with every new field. e.g. in field "order_id" each contact has 23, in the field "invoice_id" each contact has 24. The fields will be overwritten by a script but next time the user visits the site all fields gets their old (wrong) value again.

[zero-one-devteam]

The error only occurs if fingerprint tracking is enables (even if we have a custom field "fingerprint" which is unique id). Instead of the appropriate value for extended fields their IDs are inserted. I fixed this by diabling fingerprinting - which I think is a good idea anyway.