It is very sad that a miscreant purchased ownership of a bunch of WordPress plugins (Fast Secure Contact Form for WordPress included), then inserted malware to provide spam mailers. Sick! Fortunately, sharp eyes at WordFence (and others) detected the malware, and WordPress took swift action against the victimized plugins.
As Mike has sold rights to his FSCF, he is no longer supporting the software.. he did release clean end-of-life versions on the fastsecurecontactform.com site along with the explanation.