The somewhat good news here is that the exploit seems to have targeted mainly developers, despite being deployed on a major Russian news site. For instance, on Windows it looked for the configuration files of various FTP clients, including Filezilla. On Linux, it targeted configuration files such as /etc/passwd, .bash_history, .mysql_history, .pgsql_history, and .ssh. Mac users were not targeted by this exploit, but they would not be immune to a different payload utilizing the same Firefox vulnerability.
The exploit leaves no trace that it has been run on a user's local machine, making it difficult to detect. Mozilla recommended users to change all the passwords and keys for the mentioned files and programs. The company also said that users of adblock programs may have been protected, depending on their enabled ad-blocking filters.