CVE-2026-61564: critical vulnerability in WWBN AVideo-Encoder

AVideo is a video-sharing Platform. Prior to 8.1.0, the unauthenticated installer endpoint `install/checkConfiguration.php` assembles `videos/configuration.php` by interpolating request parameters, including `webSiteRootURL`, into single-quoted PHP string literals without escaping. An attacker can terminate a literal and inject PHP that executes as the web-server user when the generated, directly requestable file is loaded. Exploitation requires `videos/configuration.php` to be absent, as on every fresh deployment or after the file is removed or moved; an existing file blocks this endpoint. The supplied `systemRootPath` must contain index.php and a connection using `databaseHost`, `databaseUser`, and `databasePass` must succeed, but the attacker can point those parameters to their own database server and needs no target credentials. The write location is also derived from `systemRootPath` without a base-directory constraint. This permits arbitrary command execution, reading and overwriting files owned by the web-server user, persistent PHP code, and control over stored database connection settings. The endpoint additionally interpolates request values into streamer and configuration INSERT statements, creating a secondary SQL-injection sink. This issue is fixed in version 8.1.0.