  Recent measurements of femtoscopic correlations at NA61/SHINE unravel that
the shape of the particle emitting source is not Gaussian. The measurements are
based on L\'evy-stable symmetric sources, and we discuss the average pair
transverse mass dependence of the source parameters. One of the parameters, the
L\'evy exponent $\alpha$, is of particular importance. It describes the shape
of the source, which, in the vicinity of the critical point of the QCD phase
diagram, may be related to the critical exponent $\eta$. Its measurement hence
may contribute to the search for and characterization of the critical point of
the phase diagram.
