In wireless sensor networks, the pairwise keys shared by non-compromised nodes could be compromised, then the adversary would misuse the pairwise keys to forge message report in order to destroy secure communication or deplete the limited resource in sensor nodes. To address this issue, in this paper, an algorithm is proposed to detect misused pairwise keys. Specially, an efficient verifiable authenticator is attached to each message report. The forwarding node can detect whether the pairwise key is misused by verifying the authenticator. The security analysis and performance analysis demonstrate the efficiency of the proposed algorithm. Moreover, the proposed algorithm can be integrated with most of key pre-distribution schemes or false data filtering schemes to provide more reliable secure communication.