Sketch illustrating the polarization of the X-ray emission arising due to scattering of an intrinsically unpolarized short flare. The coordinate system is chosen so that the primary source, Sgr A*, is located at the origin, z-axis points from the observer toward it, and the xz-plane contains the center of the reflecting molecular complex (gray sphere). The line of sight and image plane positions of the cloud are connected by the parabolic relation (Eq. (1)). For an intrinsically unpolarized primary source, the electric field vector of the reflected emission is perpendicular to the scattering (i.e., xz) plane, and the polarization degree (color coded) is set by the cosine of the scattering angle θ. The inset shows the definition of the Stokes parameters used throughout the paper (with +Q and +U pointing toward the celestial north and northeast, respectively) and the predicted direction of electric field vector (red arrow).