As Extended Reality (XR) devices and applications become more mainstream, so too will XR advertising — advertising that takes place in XR mediums. Due to the defining features of XR devices, such as the immersivity of the medium and the ability of XR devices to simulate reality, there are fears that these features could be exploited to create manipulative XR ads that trick consumers into buying products they do not need or might harm them. Using scenario construction, we investigate potential future incarnations of manipulative XR advertising and their harms. We identify five key mechanisms of manipulative XR advertising: misleading experience marketing; inducing artificial emotions in consumers; sensing and targeting people when they are vulnerable; emotional manipulation through hyperpersonalization; and distortion of reality. We discuss research challenges and questions in order to address and mitigate manipulative XR advertising risks.