It is clearly a setting, because it works in other browsers. In my particular case, on my home PC ccleaner is the only browser that works. the applet is installed on all of the machines that I support, however because I use a remote RMM tool, the applet is generated on my PC through a browser, and therefore opens the remote control window in a browser. It does not matter what is on the other machines, it matters what is on my machine. There is a specific problem with CCleaner Browser that does not happen elsewhere. I was able to select open in new window, because otherwise nothing happens and I have no indicator of what is going on, however when opening in a new window it comes up as about:blank#blocked. There has to be a way to make this able to be used. Being as it is using Chromium anyway, and it works on Chrome and Edge, it is clearly a setting.
