The summer PDF spam campaign hit hard and fast. Adobe admits a critical vulnerability had been found in PDF files. Adobe is telling customers to “use caution” when clicking on attachments. The same technique could deliver Trojans, viruses, malware and other threats. It’s important to realize that the XSS vulnerability probably wont be the last attack on PDF files. It is simply too juicy a target. Still, Acrobat Reader is well-nigh universal, and that makes it a tempting target.”]
Source: https://www.csoonline.com/article/2122228/pdf-spam-storm.html