Graylog Allows Session Takeover via Insufficient HTML Sanitization

Graylog is a free and open log management platform. Prior to versions 6.0.14, 6.1.10, and 6.2.0, it is possible to obtain user session cookies by submitting an HTML form as part of an Event Definition Remediation Step field. For this attack to succeed, the attacker needs a user account with permissions to create event definitions, while the user must have permissions to view alerts. Additionally, an active Input must be present on the Graylog server that is capable of receiving form data (e.g. a HTTP input, TCP raw or syslog etc). Versions 6.0.14, 6.1.10, and 6.2.0 fix the issue. No known workarounds are available, as long as the relatively rare prerequisites are met.