fix: [Backport] excel injection backport (#8086)

apps/web/lib/utils/file-conversion.ts

@@ -2,11 +2,30 @@ import { AsyncParser } from "@json2csv/node";
 import * as xlsx from "xlsx";
 import { logger } from "@formbricks/logger";
 
+// Defang spreadsheet formula injection. Cell values starting with
+// =, +, -, @, tab, or CR are evaluated as formulas by Excel/Sheets/Numbers.
+// Sanitize at the render boundary only — never rewrite row keys, since
+// distinct user-controlled labels could collide after prefixing (e.g.
+// "=field" and "'=field" both map to "'=field"), dropping cell data.
+const FORMULA_TRIGGER = /^[=+\-@\t\r]/;
+
+const sanitizeFormulaInjection = <T>(value: T): T => {
+  if (typeof value === "string" && FORMULA_TRIGGER.test(value)) {
+    return `'${value}` as T;
+  }
+  return value;
+};
+
 export const convertToCsv = async (fields: string[], jsonData: Record<string, string | number>[]) => {
   let csv: string = "";
 
+  // Field descriptors preserve the original lookup key while overriding the
+  // rendered label and cell value with sanitized versions.
   const parser = new AsyncParser({
-    fields,
+    fields: fields.map((name) => ({
+      label: sanitizeFormulaInjection(name),
+      value: (row: Record<string, string | number>) => sanitizeFormulaInjection(row[name]),
+    })),
   });
 
   try {
@@ -23,8 +42,13 @@ export const convertToXlsxBuffer = (
   fields: string[],
   jsonData: Record<string, string | number>[]
 ): Buffer => {
+  // Build as array-of-arrays so original row keys are looked up before
+  // sanitization is applied to the rendered header/cell only.
+  const headerRow = fields.map(sanitizeFormulaInjection);
+  const dataRows = jsonData.map((row) => fields.map((name) => sanitizeFormulaInjection(row[name])));
+
   const wb = xlsx.utils.book_new();
-  const ws = xlsx.utils.json_to_sheet(jsonData, { header: fields });
+  const ws = xlsx.utils.aoa_to_sheet([headerRow, ...dataRows]);
   xlsx.utils.book_append_sheet(wb, ws, "Sheet1");
   return xlsx.write(wb, { type: "buffer", bookType: "xlsx" });
 };