arXiv subjects

Soheil Khodayari

Publications and source records attributed to Soheil Khodayari.

3 recordsLinked to original sources

arXiv2026

Indirect Prompt Injection in the Wild: An Empirical Study of Prevalence, Techniques, and Objectives

As LLMs are increasingly integrated into systems that browse, retrieve, summarize, and act on web content, webpages have become an untrusted input vector for downstream model behavior. This enables site owners, contributors, and adversaries to embed instructions directly in web resources, i.e., indirect prompt injections. While prior work demonstrates such attacks in controlled settings, their prevalence, deployment, and real-world impact remain unclear. We present one of the first large-scale empirical analyses of indirect prompt injections in webpages and HTTP responses. Analyzing 1.2B URLs from 24.8M hosts, we identify 15.3K validated instances across 11.7K pages. These are not isolated cases: a small number of recurring templates account for most cases. We characterize their objectives, delivery mechanisms, visibility, persistence, and impact, revealing a heterogeneous ecosystem spanning disruptive prompts, reputation manipulation, content-protection directives, and AI-bot detection, targeting systems such as crawlers, search pipelines, customer-support agents, and hiring workflows. A key finding is that most instructions target machines rather than humans: about 70% appear in non-rendered HTML (e.g., headers, comments, metadata), and many visible cases are hidden via rendering techniques. To assess practical risk, we run 5,200 controlled experiments across 13 models and four webpage representations. Our results show compliance is limited but non-negligible, reaching up to 8% for smaller models on plain-text inputs, while structured representations reduce compliance by preserving structural cues. Overall, prompt-based interference is already present in the web ecosystem and represents a growing source of tension between LLM-driven automation and the sites it consumes.

cs.CR↗

arXiv2024

Exploration of the Dynamics of Buy and Sale of Social Media Accounts

There has been a rise in online platforms facilitating the buying and selling of social media accounts. While the trade of social media profiles is not inherently illegal, social media platforms view such transactions as violations of their policies. They often take action against accounts involved in the misuse of platforms for financial gain. This research conducts a comprehensive analysis of marketplaces that enable the buying and selling of social media accounts. We investigate the economic scale of account trading across five major platforms: X, Instagram, Facebook, TikTok, and YouTube. From February to June 2024, we identified 38,253 accounts advertising account sales across 11 online marketplaces, covering 211 distinct categories. The total value of marketed social media accounts exceeded \$64 million, with a median price of \$157 per account. Additionally, we analyzed the profiles of 11,457 visible advertised accounts, collecting their metadata and over 200,000 profile posts. By examining their engagement patterns and account creation methods, we evaluated the fraudulent activities commonly associated with these sold accounts. Our research reveals these marketplaces foster fraudulent activities such as bot farming, harvesting accounts for future fraud, and fraudulent engagement. Such practices pose significant risks to social media users, who are often targeted by fraudulent accounts resembling legitimate profiles and employing social engineering tactics. We highlight social media platform weaknesses in the ability to detect and mitigate such fraudulent accounts, thereby endangering users. Alongside this, we conducted thorough disclosures with the respective platforms and proposed actionable recommendations, including indicators to identify and track these accounts. These measures aim to enhance proactive detection and safeguard users from potential threats.

cs.CR↗

arXiv2020

Cross-Origin State Inference (COSI) Attacks: Leaking Web Site States through XS-Leaks

In a Cross-Origin State Inference (COSI) attack, an attacker convinces a victim into visiting an attack web page, which leverages the cross-origin interaction features of the victim's web browser to infer the victim's state at a target web site. Multiple instances of COSI attacks have been found in the past under different names such as login detection or access detection attacks. But, those attacks only consider two states (e.g., logged in or not) and focus on a specific browser leak method (or XS-Leak). This work shows that mounting more complex COSI attacks such as deanonymizing the owner of an account, determining if the victim owns sensitive content, and determining the victim's account type often requires considering more than two states. Furthermore, robust attacks require supporting a variety of browsers since the victim's browser cannot be predicted apriori. To address these issues, we present a novel approach to identify and build complex COSI attacks that differentiate more than two states and support multiple browsers by combining multiple attack vectors, possibly using different XS-Leaks. To enable our approach, we introduce the concept of a COSI attack class. We propose two novel techniques to generalize existing COSI attack instances into COSI attack classes and to discover new COSI attack classes. We systematically apply our techniques to existing attacks, identifying 40 COSI attack classes. As part of this process, we discover a novel XS-Leak based on window.postMessage. We implement our approach into Basta-COSI, a tool to find COSI attacks in a target web site. We apply Basta-COSI to test four stand-alone web applications and 58 popular web sites, finding COSI attacks against each of them.

cs.CR↗