Last year, we released a post about a malware injector found in an Adobe Flash (.swf) file. In that post, we showed how a SWF file is used to inject an invisible, malicious iFrame. Now we are seeing more varieties infecting both WordPress and Joomla websites. Variable names, coding logic, and useragent condition are all indicators of this. However, the source website delivering the malicious payload is different. This time, while there were mostly Jooml based websites affected previously, were also seeing WordPress sites with this infection.”]
Source: https://blog.sucuri.net/2015/04/website-malware-the-swf-iframe-injector-evolves.html