In Windows 10, it may happen at some point, that you can’t set the default browser correctly (Chrome, Firefox, etc). Here is one possible solution to get your system to remember your default browser choice, if you are having this problem.
In your Firefox browser, if you cannot use CTRL+SHIFT+V to paste plain text without any formatting (paste special function), then one possibility is that you have a conflict with a Firefox add-on. A common conflict may be with the popular Firefox add-on AdBlock Plus. Edit preferences in Firefox to quickly fix this Firefox paste special issue.
A critical Java security bug has been found for all versions of Java 7, including fully updated versions. Until a Java update to fix this problem is available, it is best to uninstall or disable Java on your computer. Here’s how to do it, depending on your browser and Java version.