Comment 5 for bug 1633678

See also https://github.com/i-rinat/freshplayerplugin/issues/246

13.1.2.3 is a dummy version used when the wrapper can't find the plugin. Firefox caches plugin information in pluginreg.dat, and since the wrapper's doesn't change when adobe-flashplugin is installed, firefox doesn't notice anything has changed and as such doesn't update the cache.

If necessary one can trigger an update of the cache by updating the time stamp

sudo touch /usr/lib/browser-plugin-freshplayer-pepperflash/libfreshwrapper-flashplayer.so