The mining only took place for several hours on February 11th before Texthelp disabled the plugin to investigate. Government sites like the UK’s Information Commissioner’s Office also took pages down in response. As with most of these injections, your system wasn’t facing a security risk — you would have just noticed your system bogging down while searching for government info. The mining goes away the moment you visit another page or close the browser tab. The biggest hassle was for the site operators, who are now discovering that their sites are vulnerable to intruders slipping in rogue code without verification.