This paper investigates secrecy sum-rate (SSR) maximization in a downlink rate-splitting multiple access (RSMA)-enabled single-waveguide pinching-antenna system (PASS) with an external eavesdropper. The RSMA power allocation, secure common-rate allocation, and pinching-antenna (PA) positions are jointly optimized subject to transmit-power, per-user secrecy-rate, and PA-placement constraints. To tackle the resulting nonconvex problem, an alternating-optimization framework is developed, combining successive convex approximation for RSMA resource allocation with feasibility-preserving projected gradient ascent for PA-position optimization. Numerical results show that the proposed design consistently outperforms the considered benchmarks in terms of average SSR, demonstrating the benefits of joint RSMA resource and PA-position optimization for secure PASS transmission.

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