In bug 828216 we discovered that the Sibelius Scorch plugin is no longer compatible with Firefox 18 and newer on Mac OS X because we removed support for the very old quickdraw graphics model for NPAPI plugins. This plugin now crashes and all versions should be hardblocked in Firefox 18 and newer on Mac. The plugin does not need to be blocked on Windows.
smichaud, can you provide the about:plugins data for the plugin so that Jorge can construct the blocklist item?
Plugin for viewing Sibelius(tm) music scores http://www.sibelius.com
MIME Type Description Suffixes
application/x-sibelius-score Sibelius Score sib,sco
Blocked on staging: https://addons-dev.allizom.org/en-US/firefox/blocked/p261
Please test, giving time for the cache to refresh.
Confirmed staged Sibelius block is working in Firefox 18.0, 19.0b1, and 21.0a1. Tested on Mac OSX 10.7 using http://www.scoreexchange.com/scores/92265.html as the testcase.
Thanks for jumping on this all. Let's push this out on Monday, so that users aren't impacted when we unthrottle again later this week.