Fengchao Chen

Fengchao Chen, Tingmin Wu, Van Nguyen et al.

Large language model (LLM)-based agents are increasingly deployed in applications, such as trip-planning agents and web-use agents, to perform complex planning and execution tasks. Prior work has shown that LLM-based agents are vulnerable to context confusion, where external adversarial content incorporated into the agent's reasoning context may be treated as task-relevant constraints. However, external malicious content can enter the agent context via channels beyond retrieval. In this work, we introduce the User-Relayed Context Manipulation (UReCoM) attack, in which attackers manipulate benign users into relaying adversarial content within user requests, thereby relocating external adversarial content into user-provided task context. Our experimental evaluation shows that UReCoM outperforms five prompt-injection baselines (naive, context ignoring, fake completion, escape-character attacks, and combined attacks) under prevention-based (Sandwich, StruQ, and SecAlign) and detection-based defenses (Perplexity detection, DataSentinel, and CausalArmor). Additionally, UReCoM shows that LLMs can reject explicit malicious instructions more reliably than they can identify adversarial task entities, such as promotion codes, embedded within user requests. On 12 commercial LLM-based agents, we find that validation of adversarial task entities is largely prompt-driven rather than default, highlighting a design flaw in current agent frameworks. These results indicate that current defenses and deployed agents remain insufficient against user-relayed context manipulations, highlighting the need for task-entity-level prevention and default safety verification in LLM-based agents.

Fengchao Chen, Tingmin Wu, Van Nguyen et al.

Phishing campaigns involve adversaries masquerading as trusted vendors trying to trigger user behavior that enables them to exfiltrate private data. While URLs are an important part of phishing campaigns, communicative elements like text and images are central in triggering the required user behavior. Further, due to advances in phishing detection, attackers react by scaling campaigns to larger numbers and diversifying and personalizing content. In addition to established mechanisms, such as template-based generation, large language models (LLMs) can be used for phishing content generation, enabling attacks to scale in minutes, challenging existing phishing detection paradigms through personalized content, stealthy explicit phishing keywords, and dynamic adaptation to diverse attack scenarios. Countering these dynamically changing attack campaigns requires a comprehensive understanding of the complex LLM-related threat landscape. Existing studies are fragmented and focus on specific areas. In this work, we provide the first holistic examination of LLM-generated phishing content. First, to trace the exploitation pathways of LLMs for phishing content generation, we adopt a modular taxonomy documenting nine stages by which adversaries breach LLM safety guardrails. We then characterize how LLM-generated phishing manifests as threats, revealing that it evades detectors while emphasizing human cognitive manipulation. Third, by taxonomizing defense techniques aligned with generation methods, we expose a critical asymmetry that offensive mechanisms adapt dynamically to attack scenarios, whereas defensive strategies remain static and reactive. Finally, based on a thorough analysis of the existing literature, we highlight insights and gaps and suggest a roadmap for understanding and countering LLM-driven phishing at scale.

Van Nguyen, Surya Nepal, Xingliang Yuan et al.

Software vulnerabilities (SVs) pose a critical threat to safety-critical systems, driving the adoption of AI-based approaches such as machine learning and deep learning for software vulnerability detection. Despite promising results, most existing methods are limited to a single programming language. This is problematic given the multilingual nature of modern software, which is often complex and written in multiple languages. Current approaches often face challenges in capturing both shared and language-specific knowledge of source code, which can limit their performance on diverse programming languages and real-world codebases. To address this gap, we propose MULVULN, a novel multilingual vulnerability detection approach that learns from source code across multiple languages. MULVULN captures both the shared knowledge that generalizes across languages and the language-specific knowledge that reflects unique coding conventions. By integrating these aspects, it achieves more robust and effective detection of vulnerabilities in real-world multilingual software systems. The rigorous and extensive experiments on the real-world and diverse REEF dataset, consisting of 4,466 CVEs with 30,987 patches across seven programming languages, demonstrate the superiority of MULVULN over thirteen effective and state-of-the-art baselines. Notably, MULVULN achieves substantially higher F1-score, with improvements ranging from 1.45% to 23.59% compared to the baseline methods.