The transmission spectroscopy of the habitable zone exoplanet LHS 1140b using JWST/NIRISS reveals a spectral signature of unocculted stellar faculae, covering ~20% of the stellar surface. The spectrum shows a 5.8σ detection of these faculae, indicating significant stellar activity. Additionally, the analysis suggests tentative evidence of Rayleigh scattering from an N₂-dominated atmosphere, with a 2.3σ significance. Global Climate Models (GCMs) rule out H₂-rich atmospheres with >10σ confidence, while water clouds form below the transit photosphere, limiting their impact on transmission data. The observations suggest that LHS 1140b is either airless or has a high mean molecular weight atmosphere. The tentative evidence of an N₂-rich atmosphere motivates further transmission spectroscopy observations of LHS 1140b. The study highlights the importance of distinguishing between mini-Neptune and water-world scenarios for temperate exoplanets, emphasizing the need for future observations to confirm the presence of a secondary atmosphere. The results underscore the significance of transmission spectroscopy in characterizing exoplanet atmospheres and assessing habitability.The transmission spectroscopy of the habitable zone exoplanet LHS 1140b using JWST/NIRISS reveals a spectral signature of unocculted stellar faculae, covering ~20% of the stellar surface. The spectrum shows a 5.8σ detection of these faculae, indicating significant stellar activity. Additionally, the analysis suggests tentative evidence of Rayleigh scattering from an N₂-dominated atmosphere, with a 2.3σ significance. Global Climate Models (GCMs) rule out H₂-rich atmospheres with >10σ confidence, while water clouds form below the transit photosphere, limiting their impact on transmission data. The observations suggest that LHS 1140b is either airless or has a high mean molecular weight atmosphere. The tentative evidence of an N₂-rich atmosphere motivates further transmission spectroscopy observations of LHS 1140b. The study highlights the importance of distinguishing between mini-Neptune and water-world scenarios for temperate exoplanets, emphasizing the need for future observations to confirm the presence of a secondary atmosphere. The results underscore the significance of transmission spectroscopy in characterizing exoplanet atmospheres and assessing habitability.