JabRef is a desktop application for managing BibTeX and BibLaTeX libraries. Prior to 6.0-alpha.6, when jabsrv or JabRef's built-in HTTP server is enabled, the GET /better-bibtex/cayw endpoint accepts an external command query parameter and CAYWQueryParams.getCommand() passes it through CAYWResource.getCitation() into PushToSublimeText.getCommandLine(). On Unix-like systems, PushToSublimeText combines this untrusted cite-command prefix and citation keys into a string executed through sh -c by ProcessBuilder without shell escaping. A client that can cause a localhost request with application=sublime can inject shell metacharacters and execute operating-system commands as the JabRef user when a valid Sublime Text command path is configured and the victim completes the CAYW selection dialog. The built-in server is disabled by default, so exploitation requires the victim to enable it or run jabsrv. This issue is fixed in version 6.0-alpha.6.