- Additive Manufacturing, a.k.a. 3D Printing, is increasingly used to manufacture functional parts, including components of safety critical systems. Therefore, assuring part quality has become of paramount importance. In-situ infrared (IR) imaging systems are a promising solution to increase final build quality and minimize time-consuming and costly post processing and characterization. However, it also raises novel security concerns. We argue that, if compromised, the same in-situ quality control can be abused to sabotage manufactured parts. As a basis for our discussion, we first detail how IR thermography is used in open-loop and, experimentally, in closed-loop quality control for powder bed fusion (PBF) systems. We then identify malicious manipulations that an adversary can perform. We discuss the consequences of the manipulations on the manufactured part's quality. For selected attacks, we also provide experimental proof of the identified manipulations and their consequences.