In the past few weeks, you might have experienced the issue with joining WebEx Meetings on CWMS using Internet Explorer:
Cannot join internal WEBEX - Error [111] - C:\ProgramData\WebEx\WebEx\onprem_1524\atgpcext.dll seem to be unaffected
This is a new issue with IE browsers caused by Cisco WebEx Browser Extension vulnerability is described in the Cisco Security Notice found here: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170124-webex
This vulnerability was resolved by a new browser extension (for IE it is called Gpc Container Class , version 10031.6.2017.0126), but you also need to update CWMS solution to the version that resolves this defect:
CSCvc88194 Cisco WebEx Browser Extension Remote Code Execution Vulnerability
The following are the versions that introduce the fix for this issue:
2.7 MR2 Patch 1
2.6 MR3 Patch 2
2.5 MR6 Patch 4
Keep in mind that in order to apply any of these patches (depending on the version you are on), you do first need to be on the Maintenance Release the patch is released for.
For example, if you are on 2.7 MR1 version, you can't update directly to 2.7 MR2 Patch 1. Instead, you need to update to 2.7 MR2 first, and then apply the 2.7 MR2 Patch 1.
Keep in mind that after you update the system, you will need to distribute PT, Meeting, and NBR Player clients to end users (if they don't have admin rights on their machines). New Meeting Client is necessary for this issue to be fully resolved.