When trying to display the CAS overview statistics, Firefox displays an unresponsive script error or an error stating invalid json string. This issue has been reported in 18.104.22.168 but it has been seen in prior releases of the code.
The json error is due to badly terminated json string. it is quite likely
the flood of virus info to the stats is causing this.
The last line should be:
Basically missing the closing "}"
hence parsing error.
Bug 231680 has been raised up to engineering to fix this issue.