Addendum to "Quantum secret sharing between multiparty and multiparty   without entanglement"
  Recently, Yan and Gao proposed a quantum secret sharing protocol between multiparty ($m$ members in group 1) and multiparty ($n$ members in group 2) using a sequence of single photons (Phys. Rev. A \textbf{72}, 012304 (2005)). We find that it is secure if the quantum signal transmitted is only a single photon but insecure with a multi-photon signal as some agents can get the information about the others' message if they attack the communication with a Trojan horse. However, security against this attack can be attained with a simple modification. 
Fu-Guo Deng, Feng-Li Yan, Xi-Han Li, Chun-Yan Li, Hong-Yu Zhou and   Ting Gao