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fix(frontend): neutralise spreadsheet formula injection in CSV export (#83) #86

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Merged
amar-python merged 1 commit into from
Oct 26, 2026
Merged

fix(frontend): neutralise spreadsheet formula injection in CSV export (#83) #86

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26 changes: 26 additions & 0 deletions csv-table-hub-main/src/__tests__/export.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,32 @@ describe("downloadErrorReport CSV", () => {
// value should be quoted
expect(text).toContain('"say ""hello"", world"');
});

// #83: user-supplied values must not run as formulas when the CSV is opened.
it.each([
['=HYPERLINK("http://x","y")', '\'=HYPERLINK(""http://x"",""y"")'],
["+cmd|' /C calc'!A0", "'+cmd|' /C calc'!A0"],
["-2+3", "'-2+3"],
["@SUM(A1:A2)", "'@SUM(A1:A2)"],
])("neutralises formula payload %s", async (value, expected) => {
const rows = buildErrorRows("data.csv", [{ rowNumber: 1, column: "c", value, reason: "test" }]);
downloadErrorReport("data.csv", rows, "csv");
const text = await cap.blob!.text();
expect(text).toContain(expected);
expect(text).not.toMatch(
new RegExp(`,${value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")}(,|$)`, "m"),
);
});

it("leaves plain negative and signed numbers unchanged", async () => {
const rows = buildErrorRows("data.csv", [
{ rowNumber: 1, column: "n", value: "-5", reason: "+3.2" },
]);
downloadErrorReport("data.csv", rows, "csv");
const text = await cap.blob!.text();
expect(text).toContain(",-5,");
expect(text).toContain(",+3.2,");
});
});

// ─── downloadErrorReport — XLSX ────────────────────────────────────────────────
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11 changes: 9 additions & 2 deletions csv-table-hub-main/src/lib/export.ts
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Expand Up @@ -40,9 +40,16 @@ export type AuditReportRow = {

// ─── CSV ──────────────────────────────────────────────────────────────────────

// Cells starting with these characters are run as formulas by Excel/Sheets
// (OWASP "CSV injection"). Report cells hold user-supplied CSV values, so
// prefix them with a quote. Plain numbers like -5 or +3.2 are left alone.
const FORMULA_START = /^[=+\-@\t\r]/;
const PLAIN_NUMBER = /^[+-]?\d+(\.\d+)?$/;

function escapeCsv(v: unknown): string {
const s = v === undefined || v === null ? "" : String(v);
return /[",\n]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
let s = v === undefined || v === null ? "" : String(v);
if (FORMULA_START.test(s) && !PLAIN_NUMBER.test(s)) s = `'${s}`;
return /[",\n\r]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
}

function toCsvBlob(headers: string[], rows: Record<string, unknown>[]): Blob {
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