Measuring Users' Security and Privacy Concerns About Third-Party Community Bots on Discord

Third-party community-based bots are central to how social platforms such as Discord work. They moderate content, manage roles, play music, and support AI-assisted conversations across millions of servers. Yet when a bot is installed in a server, it can access messages, user profiles, and server metadata concerning members who did not participate in the installation decision, with no standardized way to communicate the associated security and privacy implications. In this paper, we analyze 23,102 third-party Discord bots and 183,142 user reviews spanning 49 detected languages and five years of feedback (2021-2026). We employ LLM-based knowledge distillation and fine-tune a DeBERTa-based classifier to identify candidate security and privacy (S&P)-relevant reviews. After manually validating the complete classifier-positive set, we retain 8,832 reviews identified as S&P-relevant, representing an observed pipeline yield of 4.82%, and map them to a 31-theme S&P taxonomy extending prior work. Our results show that S&P-related reviews focus heavily on Data Sharing (30.5%) and Data Collection (16.2%). Confession and anonymity bots have pipeline-identified SPRRs above 50%, more than ten times the ecosystem-wide pipeline yield of 4.82%. Star ratings may obscure the frequency and valence of S&P-related discussion, while conventional metadata features, such as permission count and administrator status, show only weak associations with user-reported S&P concerns. We then build BotLens, a proof-of-concept auditing framework that combines review-derived S&P signals with bot metadata to provide on-demand decision support for the community-based bot ecosystem. BotLens exposes six tools through a Model Context Protocol server, supporting bot-level checkups, server-wide comparison, and integration with AI agents.