GROBID is machine learning software for extracting information from scholarly documents. Prior to 0.9.1, the Linux non-server PDF conversion path in grobid-core/src/main/java/org/grobid/core/document/DocumentSource.java passes an attacker-influenced PDF filename through DocumentSource.pdfalto, which interpolates the path into a bash -c command string. A single quote in the filename can terminate the intended quoting, and ProcessRunner.run in grobid-core/src/main/java/org/grobid/core/process/ProcessRunner.java starts the resulting command through ProcessBuilder, allowing arbitrary commands to execute with GROBID process privileges. The bundled REST server path is not affected. This issue is fixed in version 0.9.1.