fish-shop/syntax-check is a GitHub action for syntax checking fish shell files. Improper neutralization of delimiters in the pattern input (specifically the command separator ; and command substitution characters ( and )) mean that arbitrary command injection is possible by modification of the input value used in a workflow. This has the potential for exposure or exfiltration of sensitive information from the workflow runner, such as might be achieved by sending environment variables to an external entity. It is recommended that users update to the patched version v1.6.12 or the latest release version v2.0.0, however remediation may be possible through careful control of workflows and the pattern input value used by this action.