Large language models (LLMs) are widely used to answer users’ information needs: users ask LLMs about the weather, pose educational questions, and consult them for legal assistance. One particularly understudied area is digital security and privacy (S P), where users may seek LLMs’ help on how to secure their online accounts or protect their computers from cyber attacks. To the best of our knowledge, no prior study has collected or analyzed the S P questions users ask LLMs; prior research on LLM response quality relied on expert-authored S P misconceptions or FAQs rather than user queries. Drawing from WildChat, a dataset of 3.2M user-LLM conversations collected in the wild, our study identifies 14,727 S P prompts and categorizes them into nine categories covering a wide range of S P topics. We sampled 450 S P prompts, and performed a thematic analysis to characterize the S P questions users ask LLMs. Separate from the thematic analysis, we curated 270 advice-seeking S P prompts, where users ask for recommendations, guidance, or specific S P information. We measured LLM response quality and consistency when posing each prompt to the LLMs 10 times. We found that commercial LLMs outperform open-weight models (GPT 5.5 provided "good enough" responses on 98% of prompts; Llama 4 on 47%). However, among prompts that received high-quality responses on average, commercial models sometimes produce semantically inconsistent responses across runs (some are contradictory, and others are different in specificity), thereby risking confusing or misleading users.