Mozilla blocks all Flash by default in Firefox because recently unearthed bugs in Flash were being used actively by the hackers and cyber-thieves. Also, Alex Stamos, Facebook’s newly appointed security chief publicly called for Adobe to kill off Flash.

“The bugs were detailed in a cache of documents stolen from security firm Hacking Team that was hit by attackers last week.”

Why Mozilla blocks all flash by default in Firefox?

Flash is widely used on many sites for multimedia and interactive elements. Adobe said it took Flash’s security very seriously and was planning to fix the bugs as soon as possible. Mozilla blocks all flash by default in Firefox and said in its support pages that the block would remain until “Adobe releases an updated version to address known critical security issues”. The company also said that the attackers used the vulnerabilities in Adobe Flash to install malicious software on users’ computers and other devices to steal their confidential data.

The Top 10 applications which are used by criminals to hack computers and steal important data; include Flash and other products by Adobe because they are used on so many devices on a regular basis.

Mark Schmidt, Senior Firefox Support Lead wrote “Even sans non-vulnerable update, we should consider the risks of blocking the vulnerable Flash versions (i.e. all of them) vs. allowing millions of people to use actively exploited versions of Flash without so much as a warning.”

Mozilla blocks all Flash by default in Firefox and has also given advice to its users regarding the Firefox’s settings adjustment so that Flash will run only with the authority of the browser’s user instead all the time. The company also said that the users should activate Flash only on the sites they trust. Firefox is one of the most popular desktop browsers among the users.