  Most baryonic matter resides in the intergalactic medium (IGM), a diffuse gas
primarily composed of ionized hydrogen and helium, filling the space between
galaxies. Observations of such an environment are crucial to better
understanding the physical processes involved in such an environment. We
present an analysis of the IGM absorption using blazar spectra from the first
eROSITA all-sky survey (eRASS1) performed onboard of the
Spectrum-Roentgen-Gamma mission (SRG) and {\it XMM-Newton} X-ray observations.
First, we fitted the continuum spectra using a log-parabolic spectrum model and
fixed the Galactic absorption. Then, we included a collisional ionization
equilibrium model, namely {\tt IONeq}, to account for the IGM absorption. The
column density $N({\rm H})$ and metallicity ($Z$) were set as free parameters.
At the same time, the redshift of the absorber was fixed to half the blazar
redshift as an approximation of the full line-of-sight absorber. We measured
IGM-$N({\rm H})$ for 147 sources for SRG and 10 sources for {\it XMM-Newton}.
We found a clear trend between IGM-$N({\rm H})$ and the blazar redshifts which
scales as $(1+z)^{1.63\pm 0.12}$. The mean hydrogen density at $z=0$ is
$n_{0}=(2.75\pm 0.63)\times 10^{-7}$ cm$^{-3}$. The mean temperature over the
redshift range is $\log(T/K)=5.6\pm 0.6$ while the mean metallicity is
$Z=0.16\pm 0.09$. We found no acceptable fit using a power-law model for either
temperatures or metallicities as a function of the redshift. These results
indicate that the IGM contributes substantially to the total absorption seen in
the blazar spectra.
