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Russia-Aligned Hackers Use GuardBreaker Prompt Injection to Disrupt AI Malware Analysis

Russia-aligned group UAC-0099 embeds GuardBreaker prompt injection in a VBScript comment to make AI malware scanners refuse analysis of a MATCHBOIL loader.

ESET identified a UAC-0099 VBScript used in an early-stage intrusion against a target in Ukraine that hides a safety-triggering comment (a question about building a nuclear weapon) intended to make AI code scanners refuse to continue analysis. The script downloads MATCHBOIL, a loader associated exclusively with UAC-0099, alongside familiar anti-analysis checks for IDA and Wireshark. The technique turns the AI triage process itself into the attack target, risking missed detections or benign misclassification of malicious samples.

Cyber Security News · 5d agoThreat actor in the wild 3 sources

Hackers Weaponize AI Safety Guardrails to Hide Malware From LLM-Powered Security Scanners

ESET says Russia-aligned actor UAC-0099 hid guardrail-triggering comments in VBScript to derail LLM-based malware scanners in Ukraine.

ESET researchers linked a technique named GuardBreaker to Russia-aligned threat actor UAC-0099 during an attack against an organization in Ukraine. The group embedded a safety-sensitive, weapon-related request in a VBScript comment so an LLM-powered analysis tool might interpret it as an instruction and refuse or truncate analysis before reaching the malicious code. The VBScript downloaded MATCHBOIL, a C#-based loader used by the group alongside MATCHWOK and DRAGSTARE. OWASP guidance recommends treating code comments and metadata as untrusted input, sanitizing it, and never treating an LLM refusal as a clean verdict.

GBHackersupdated · 5d agofirst · 5d agoThreat actor in the wild 3 sources1

GuardBreaker: Derailing AI-assisted malware analysis with a code comment

ESET names 'GuardBreaker': UAC-0099 embeds a nuclear-weapon question in VBScript comments to trip LLM scanner guardrails during analysis of its MATCHBOIL loader.

ESET researchers observed the Russia-aligned group UAC-0099 inserting a decoy prompt injection into a VBScript used to install its MATCHBOIL loader in an attack against a Ukrainian target, aiming to make LLM-based code scanners refuse and stop inspecting the file. The comment triggers safety guardrails with a request about building a nuclear weapons but has no runtime effect. Similar LLM-thwarting tricks have appeared in malicious PyPI and npm packages reported by Socket and StepSecurity. ESET recommends multi-model cross-validation of AI-assisted analysis and treating missing LLM output as requiring further checks.

ESET WeLiveSecurityupdated · 5d agofirst · 6d agoAI safety & security 3 sources1

ConnectWise Patches ScreenConnect Vulnerability Exploited in Worm-Like Attacks

ConnectWise patched critical ScreenConnect flaw CVE-2026-84869 (CVSS 9.9) exploited since August 20 in worm-like attacks; CISA added it to KEV.

ConnectWise released urgent patches for CVE-2026-84869 (CVSS 9.9), a missing authorization and improper privilege management flaw in ScreenConnect allowing file transfer and execution through active remote sessions without host confirmation. Huntress reported in-the-wild exploitation since August 20, with attackers using rogue ScreenConnect clients to push four VBScript files for persistence and worm-like propagation to other ScreenConnect clients. The flaw is fixed in ScreenConnect 26.6.5, with disabling the TransferFiles permission as a temporary mitigation. CISA added the CVE to its KEV catalog, requiring federal agencies to patch within three days under BOD 26-04.

SecurityWeekupdated · 10h agofirst · 2d agoExploit / PoC in the wild 4 sourcesCVE-2026-848691

U.S. CISA adds GitLab, JFrog Artifactory, and ConnectWise ScreenConnect flaws to its Known Exploited Vulnerabilities catalog

CISA added four actively exploited GitLab, JFrog Artifactory, and ConnectWise ScreenConnect flaws to the KEV catalog with imminent deadlines.

CISA added CVE-2026-42016 and CVE-2026-42018 (JFrog Artifactory), CVE-2026-84869 (ConnectWise ScreenConnect), and CVE-2026-85706 (GitLab, CVSS 10.0) to its KEV catalog. Artifactory flaws are being chained with CVE-2026-82329 in attacks observed August 15 to September 8, taking over self-hosted servers, creating persistent administrator accounts, and installing backdoors. ScreenConnect CVE-2026-84869 allows unauthorized file transfer and execution during remote sessions, linked by Huntress to malicious VBScript deliveries, and is fixed in version 26.6.5. GitLab's repository commits API path traversal exposes SSH keys, database credentials, deploy tokens, and CI/CD variables, with watchTowr already observing in-the-wild probes. Federal agencies must patch GitLab and ScreenConnect flaws by September 14, 2026, and Artifactory flaws by September 25, 2026.

CISA Adds 5 Actively Exploited Artifactory, ScreenConnect, and RouterOS Flaws to KEV

CISA added five actively exploited JFrog Artifactory, ConnectWise ScreenConnect, and MikroTik RouterOS flaws to its KEV catalog.

CISA added five actively exploited vulnerabilities to the KEV catalog: CVE-2026-42016 and CVE-2026-42018 in JFrog Artifactory, CVE-2026-84869 in ConnectWise ScreenConnect (CVSS 9.9), and CVE-2026-67277 and CVE-2026-86060 in MikroTik RouterOS. The Artifactory bugs are chained with CVE-2026-82329 to gain administrative control, deploy malicious Groovy plugins, and install Rust-based backdoors. CERT Polska dubbed the RouterOS chain 'MikroTrick'; FCEB agencies must patch between September 13 and 25, 2026.

The Hacker Newsupdated · 2d agofirst · 4d agoExploit / PoC in the wild 2 sourcesCVE-2026-42016CVE-2026-42018CVE-2026-84869+3 CVEs2· 1 read