S9Y » Serendipity : Security Vulnerabilities, CVEs, Published In April 2017 (XSS)

Stored XSS in Serendipity v2.1-rc1 allows an attacker to steal an admin's cookie and other information by composing a new entry as an editor user. This is related to lack of the serendipity_event_xsstrust plugin and a set_config error in that plugin.