The advances of network technologies and digital devices facilitate users to exchange multimedia data over the public networks. However, this also raises significant concerns about how to protect sensitive multimedia data from being illegally modified. Therefore, this paper proposes a fragile watermarking scheme to detect illegitimate alterations of a watermarked image. The proposed method hides a magic square into a grayscale image in a block-by-block fashion by using the least significant bit replacement. Experimental results show that the watermarked image produced by the proposed method has a good visual quality. In addition, the proposed approach can successfully and exactly detect and localize any tampered regions of watermarked images. Furthermore, the proposed scheme can approximately recover those tampered regions.