When I clear data/cache, there is still 1.2mb of data, but nothing shows up in manage exceptions for at least the last two versions of firefox. I'm guessing this a false positive, I use linux mint, and have investigated data under my .mozilla folder, I don't see anything there. I clear data as I don't trust the browser to do it even though I have it checked to clear. Guessing I'm not the only one seeing this.
