fix: properly set string values in exports to escape formulas

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

lib/Service/SubmissionService.php

@@ -339,11 +339,12 @@ private function exportData(array $header, array $data, string $fileFormat, ?Fil
 						->getAlignment()
 						->setWrapText(true);
 				} else {
-					$activeWorksheet->setCellValue([$column, $row], $value);
-
-					// Quote cell values that start with '=' to prevent evaluation of formulas
+					// Explicitly set the type of the value to string for values that start with '=' to prevent it being interpreted as formulas
 					if (is_string($value) && str_starts_with($value, '=')) {
-						$activeWorksheet->getCell([$column, $row])->getStyle()->setQuotePrefix(true);
+						$activeWorksheet->getCell([$column, $row])
+							->setValueExplicit($value);
+					} else {
+						$activeWorksheet->setCellValue([$column, $row], $value);
 					}
 				}
 			}