VW Coaching Pro Theme Flagged by client as a potential security risk

Hi
One of my clients has reported that their internal access to their website has been blocked because the site has potential malware content.
The file that has been flagged is … /vw-coaching-pro/assets/js/tether.js?ver=6.3.1
The site has version 1.1.1 of the theme and Version 6.3.1 of WordPress.
The software flagging the file is Quttera who have flagges the file as suspicious with a threat of S.Hidden.Iframe.gen.
These are the details…
Detected Suspicious Files
File name fdetraining.co.uk/wp-content/themes/vw-coaching-pro/assets/js/tether.js?ver=6.3.1
Threat name S.Hidden.Iframe.gen
File type ASCII
Reason Detected hidden iframe tag to ‘bugzilla.mozilla.org’
Details Detected hidden reference to external web resource.
Threat dump [[<iframe>-like). function getActualBoundingClientRect(node) { var boundingRect = node.getBoundingClientRect(); // The original object returned by getBoundingClientRect is immutable, so we clone it // We can’t use extend because the properties are not considered part of the object by hasOwnProperty in IE9 var rect = {}; for (var k in boundingRect) { rect[k] = boundingRect[k]; } if (node.ownerDocument !== document) { var _frameElement = node.ownerDocument.defaultView.frameElement; i]]

Can you advise if this code is should be there and if so what its purpose is?

The following link points to the full Quttera report for more details.
https://quttera.com/detailed_report/www.fdetraining.co.uk#suspicious_files_accord_value