Dr. Xiaoyuan Zhang works as a postdoc researcher at Max-Planck Institute for extraterrestrial Physics. He obtained his PhD degree in Leiden University and the Netherlands Institute for Space Research in June 2022. He has research interests in multiple aspects of galaxy clusters and ICM astrophysics, including thermodynamic properties and mass accretion in galaxy cluster outskirts, particle acceleration in the ICM, and properties of the hot gas in large scale structures.The highly ionized warm/hot intergalactic medium (WHIM) permeating the vast space of the cosmic filaments is one of the least explored baryon contents in the local Universe. Technological limitations hamper X-ray emission studies suited to finding the warmer phase of the WHIM. Therefore, they have been focused mostly on volume-limited astrophysical objects, such as individual <10>80% of the total filament volume and 50% of the baryonic mass, remain to be explored. In this work, we examine the emission properties of the WHIM in long cosmic filaments using the deepest SRG/eROSITA All-Sky Survey data available. By stacking the X-ray emission from ～8000 cosmic filaments traced by the galaxy distribution by the Sloan Digital Sky Survey, we detect the X-ray emission in the filament extending out to 10 Mpc from the spine at an 8.9 sigma significance. After correcting for the emission from the unresolved point sources and extended low-mass haloes, the detection of the WHIM component remains statistically significant at a 5.3 sigma level. We further stack the eROSITA X-ray spectra and obtain the first-ever broadband 100 eV resolution spectrum of cosmic filaments at the source frame. The best-fit mean gas temperature of the WHIM component is 10^6.8 K.