A cross site scripting (XSS) vulnerability exists in CheckMK versions 1.4.0x prior to 1.4.0p6, allowing an unauthenticated remote attacker to inject arbitrary HTML or JavaScript via the username parameter when attempting authentication to webapi.py, which is returned unencoded with content type text/html.

A cross site scripting (XSS) vulnerability exists in CheckMK versions 1.2.8x prior to 1.2.8p25 and 1.4.0x prior to 1.4.0p9, allowing an unauthenticated attacker to inject arbitrary HTML or JavaScript via the outputformat parameter, and the username parameter of failed HTTP basic authentication attempts, which is returned unencoded in an internal server error page.