The Mozilla Firefox web browser is used by roughly 30% of all Internet users. The company is seriously concerned about the Security of its users for many years. Mozilla announced back in that it planned to enable ” feature in upcoming Firefox versions, which will block most vulnerable plugins likeby default. The feature will only start blocking by default, no sooner than Firefox 30. If accepted, the plugin will be whitelisted for next 4 Firefox releases i.e. 30 weeks (6 weeks in beta version and 24 weeks in the general release channel), with the possibility to apply for a further extension later.
Source: https://thehackernews.com/2014/03/Firefox-click-to-play-plugin-security.html