That is almost 800,000 reported bugs in more than 14 years of the history of Bugzilla (I am mentioning "almost" since the bug count does not start with bug number "1", but with bug number "507"). Of course, Firefox does not reach quite that far back as the first pre-release version did not arrive until September 2002 and the first final release until November 2004. Bugzilla's origins date back to 1998 when the bugtracker was released as open source software by Netscape.
Nevertheless, the number of bugs filed by Firefox developers is impressive.
Of the 799,493 listed bugs (until October 10), more than half a million (530,953) were filed between the release of Firefox 1 on November 9, 2004 and October 10, 2012. Prior to the release of the first final browser, the database already included 268,033 bugs. The most recent 100,000 bugs were filed between November 4, 2011 and October 10, 2012. That bug filing rate puts the Mozilla community on a pace of 293 bugs filed per day.