In their recent paper [Phys. Rev. Lett. 110, 173601 (2013)] a group of RCPTM scientists (K. Bartkiewicz, K. Lemr, A. Černoch and J. Soubusta) shows that their optimal cloning device with high-success rate makes the eavesdropping on quantum-cryptography communications possible. Quantum cryptography offers the highest level of security of a communication line by using laws of quantum physics that prevent perfect cloning. Technical imperfections of practical devices, however, open space for approximate cloning devices allowing to hide the attack in usual transmission losses. This work was also featured in a recent issue of New Scientist (issue 2915, 03 May 2013).