I don't know if WhatsApp Plus contain any malware or not. But i read a news about the other mod named fmwhatsapp which is similar to whatsapp plus.
Kaspersky researchers scanned the FMWhatsApp's code and found the Triada Trojan along with the Advertising SDK. Triada trojan is hard to find as it resides in the RAM.
Now you can decide yourself whether you want to use or not.