An issue was discovered in the Cisco WebEx Extension before 1.0.7 on Google Chrome, the ActiveTouch General Plugin Container before 106 on Mozilla Firefox, the GpcContainer Class ActiveX control plugin before 10031.6.2017.0126 on Internet Explorer, and the Download Manager ActiveX control plugin before 2.1.0.10 on Internet Explorer. A vulnerability in these Cisco WebEx browser extensions could allow an unauthenticated, remote attacker to execute arbitrary code with the privileges of the affected browser on an affected system. This vulnerability affects the browser extensions for Cisco WebEx Meetings Server and Cisco WebEx Centers (Meeting Center, Event Center, Training Center, and Support Center) when they are running on Microsoft Windows. The vulnerability is a design defect in an application programing interface (API) response parser within the extension. An attacker that can convince an affected user to visit an attacker-controlled web page or follow an attacker-supplied link with an affected browser could exploit the vulnerability. If successful, the attacker could execute arbitrary code with the privileges of the affected browser.