Trivy Action has a script injection via sourced env file in composite action

Summary

Trivy Action runs Trivy as GitHub action to scan a Docker container image for vulnerabilities. A command injection vulnerability exists in `aquasecurity/trivy-action` versions 0.31.0 through 0.33.1 due to improper handling of action inputs when exporting environment variables. The action writes `export VAR=<input>` lines to `trivy_envs.txt` based on user-supplied inputs and subsequently sources this file in `entrypoint.sh`. Because input values are written without appropriate shell escaping, attacker-controlled input containing shell metacharacters (e.g., `$(...)`, backticks, or other command substitution syntax) may be evaluated during the sourcing process. This can result in arbitrary command execution within the GitHub Actions runner context. Version 0.34.0 contains a patch for this issue. The vulnerability is exploitable when a consuming workflow passes attacker-controlled data into any action input that is written to `trivy_envs.txt`. Access to user input is required by the malicious actor. Workflows that do not pass attacker-controlled data into `trivy-action` inputs, workflows that upgrade to a patched version that properly escapes shell values or eliminates the `source ./trivy_envs.txt` pattern, and workflows where user input is not accessible are not affected.