The other prong of this attack uses CBC malleability gadgets, tools that are able to edit cipher texts encrypted with the cipher block chaining (CBC) encryption mode without integrity checks. It just so happens that the PDF standard does exactly that. This method can modify plain text as well as add in new encrypted content to the file. This technique can enact the PDF forms and hyperlink techniques as listed in the Direct Exfiltration method. The CBC Gadgets method can also edit PDF object streams such that they submit themselves to an attacker controlled server. Both attacks require the victim to open the tainted document so that the traps can deliver the finally decrypted information to the attacker. The researchers have tested their techniques on 27 PDF viewers and all were susceptible to at least one method of the PDFex attack.