T09 · Insecure Skill Coding Practices
- Location
scripts/fetch_tase_data.sh:36- Finding
User-Controlled Ticker Permits jq Filter Injection
- Content
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Vulnerability Details
File Location:
scripts/fetch_tase_data.sh, lines 36-45
Vulnerability Type: Dynamic jq program construction using untrusted input
Risk Level: HighVulnerable Code
sh echo "$result" | jq '{ source: "Finnhub", ticker: "'$ticker'", price: .c, high: .h, low: .l, open: .o, volume: .v, currency: "ILS" }'Technical Analysis
The user-controlled
$tickervalue is concatenated directly into ajqfilter rather than supplied as a data argument. Although shell quoting limits direct shell metacharacter interpretation, quotation marks and valid jq syntax within the ticker can terminate the intended string and alter the jq program.A crafted ticker can inject jq expressions that manipulate the generated response or access jq features such as
$ENV, which exposes environment variables inherited by the jq process. This may allow disclosure ofFINNHUB_API_KEYand other secrets present in the script's environment.This is jq-language injection rather than direct shell-command injection. The demonstrated scope is response manipulation, environment-variable disclosure, and processing disruption; the affected code does not establish arbitrary operating-system command execution.
Attack Path
- An attacker supplies a specially crafted ticker or security identifier to the Skill.
- The Skill invokes
fetch_tase_data.shwith the attacker-controlled value. - The script normalizes the identifier but does not restrict it to a safe ticker character set.
- A successful Finnhub response reaches the vulnerable jq operation.
- The ticker is inserted into the jq filter as executable syntax.
- The injected expression accesses
$ENV, changes the output structure, or causes the filter to fail. - Sensitive environment values or attacker-controlled output may be printed and subsequently returned by the Agent.
Impact Assessment
An ...[truncated 515 chars]
- Remediation
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Remediation Suggestions
Pass the ticker to jq as data with
--argrather than concatenating it into jq source:sh echo "$result" | jq --arg ticker "$ticker" '{ source: "Finnhub", ticker: $ticker, price: .c, high: .h, low: .l, open: .o, volume: .v, currency: "ILS" }'Apply the same pattern to every jq invocation and construct fallback JSON with
jq -n --argrather than interpolated shell strings.Validate ticker input before any network request or structured-data processing. For example, permit only the character set and length required by supported identifiers:
sh if [[ ! "$TICKER" =~ ^[A-Z0-9._-]{1,32}$ ]]; then echo '{"error":"Invalid ticker format"}' exit 1 fiAdditional hardening should include:
- Invoke the Python implementation instead of maintaining a separate dynamically constructed jq path.
- Run the script with a minimal environment containing only required variables.
- Add regression tests using quotation marks, jq operators, Unicode input, and malformed identifiers.
- Ensure error output cannot accidentally include inherited environment variables.