The issue applies to some people and not others but the root of the issue if is the problem is to turn back on Windows Cleartype font or disable Hardware Acceleration which is for your Video Card. The issue sounds like it is so please turn on your Cleartype font. https://www.nytimes.com/2016/09/21/technology/personaltech/get-sharper-text-on-your-windows-screen.html Contact WebEx Support : cisco.chromestore@gmail.com or visit their support page for tools and articles : https://support.webex.com/MyAccountWeb/supporthome.do as is listed on their Extension Page : https://addons.mozilla.org/en-US/firefox/addon/cisco-webex-extension/ You could try the 7min fix if it works : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Reinstall with Current Release Firefox 59.0.1 with a Full Version Installer *https://www.mozilla.org/firefox/all/ Please let us know if this solved your issue or if need further assistance.