KBI 311805 Issue Addressed: Some Web Pages Failed To Load With Jscript Error Of Undefined Property PageRequestManager


Argent Advanced Technology 5.1A-2001-A and below


Wednesday, 15 April 2020


When Argent Sentinel records a web session, the web page might load blank, partially, or disabled so that the user cannot click on any element on the page

On further checking the console output in DevTools, Jscript errors are shown, such as:

Cannot read property ‘PageRequestManager’ of undefined

The affected web sites are usually ones developed with ASP.NET web forms using Telerik components

The issue is caused by the web site not recognizing Argent Sentinel as valid user agent

The issue has been addressed in Argent AT 5.1A-2004-A

Technical Background

Argent Sentinel uses “Argent Defender Ultra” as the default user agent string

The ASP.NET engine of the affected web site does not recognize this string, so it believes that the browser does not support Ajax

This results in the ScriptManager not including “MicrosoftAjaxWebForms.js” and other issues related to Ajax panels not loading

Argent Sentinel 5.1A-2004-A allows a custom user agent string

By setting it to ‘Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0’ or other common browser user agents, affected web sites can be recorded normally


Upgrade to Argent Advanced Technology 5.1A-2004-A or above