file extention validation not working on windows but working on mac

Question

async upload(
        @UploadedFile() file: Express.Multer.File,
        @Body() body: FileUploadDto,
      ) {
        const forbiddenExt = [
          '.exe',
          '.bat',
        ];
           const fileName = file.filename || file.originalname;
          const fileExtension = fileName
            .slice(((fileName.lastIndexOf('.') - 1) >>> 0) + 2);
    
          const hasForbiddenExtension = forbiddenExt.includes(fileExtension);
    
          if (hasForbiddenExtension) {
            throw new HttpException(
              'File type is not supported. Upload only .apk or .ipa',
              400,
            );
          }
        
          const response = await this.uploadFile(
            `${
              body.filename
            }`,
            file.buffer,
          );

          return {
            success: true,
          };
    }

above code works fine on mac its validating .exe file properly but windows I'm able to upload .exe files still how to avoid? validation not working only on windows

Answer 1

Need to normalize the fileExtension

const fileName = file.filename || file.originalname;
      const fileExtension = fileName
        .slice(((fileName.lastIndexOf('.') - 1) >>> 0) + 2)
        .toLowerCase();
      const normalizedExtension = fileExtension.startsWith('.')
        ? fileExtension
        : `.${fileExtension}`;