A vulnerability, which was classified as problematic, has been found in YAFNET up to 3.1.10. This issue affects some unknown processing of the file /forum/PostPrivateMessage of the component Private Message Handler. The manipulation of the argument subject/message leads to cross site scripting. The CWE definition for the vulnerability is CWE-79. The weakness was published 01/27/2023 by Chun-Li Lin with CHT Security Co., Ltd. as 2237a9d552e258a43570bb478a92a5505e7c8797. The advisory is shared at drive.google.com. The identification of this vulnerability is CVE-2023-0549. The attack may be initiated remotely. Technical details are available. Furthermore, there is an exploit available. The exploit has been disclosed to the public and may be used. The price for an exploit might be around USD $0-$5k at the moment. MITRE ATT&CK project uses the attack technique T1059.007 for this issue. It is declared as proof-of-concept. The exploit is available at drive.google.com. We expect the 0-day to have been worth approximately $0-$5k. Upgrading to version 3.1.11 is able to address this issue. The updated version is ready for download at github.com. The identifier of the patch is 2237a9d552e258a43570bb478a92a5505e7c8797. The bugfix is ready for download at github.com. It is recommended to upgrade the affected component. A possible mitigation has been published even before and not after the disclosure of the vulnerability.