The vulnerability is an Improper Neutralization of Input During Web Page Generation that results in Stored Cross‑Site Scripting (CWE‑79). It allows an attacker to inject malicious script content that is stored and later presented to users in the web interface, potentially causing the script to execute in the browsers of users who view the affected page. The resulting impact includes the possibility of session hijacking, data theft, or defacement of the web interface, depending on the privileges of the user accessing the malicious content.

Forcepoint Web Security (On‑Prem) on Windows is affected for all versions up to and including 8.5.6. The vendor explicitly states that the issue does not exist in version 8.5.7 or newer.

The CVSS score of 4.8 indicates moderate severity; no EPSS score is available and the vulnerability is not listed in CISA’s KEV catalog, suggesting no publicly known exploitation in the wild. Based on the description, the likely attack vector is through a web interface that accepts user‑supplied data and stores it pending rendering, implying that an attacker would need either authenticated access to the management console or an ability to submit content that is later served to users. The exploit would work only if the vulnerable stored content is displayed to a victim’s browser.