Flare published a deep profile of REMUS, the 64-bit infostealer that emerged in early 2026 after Lumma Stealer's core operators were doxxed in late 2025. Gen Threat Labs links REMUS directly to Lumma's codebase through 'Tenzor' transitional builds from September 2025, identical string obfuscation, anti-VM checks via cpuid leaf 0x40000000, and a refined Application-Bound Encryption bypass for Chromium browsers. The malware harvests browser passwords, cookies, autofill, crypto wallets, and clipboard data, and uses EtherHiding (blockchain-based C2 resolution) for resilience. Flare's 128-post analysis of REMUS forum activity from Feb 12 to May 8 shows the operation has moved from rapid feature expansion into platform stabilization, with active customer-facing MaaS development.
Two days after the Mini Shai-Hulud worm tore through TanStack and Mistral AI packages, the named-victim count grew sharply. OpenAI confirmed that two employee devices were compromised through the TanStack supply-chain chain and that a limited subset of internal source code repositories had credential material exfiltrated; the company is rotating its macOS code-signing certificates and tells Mac users they must update ChatGPT Desktop, Codex, and Atlas apps by June 12, 2026, or the apps will stop launching. TeamPCP separately listed 450 Mistral AI private repositories on a criminal forum for 25,000 dollars. Mistral confirmed a codebase management system was temporarily compromised on May 12 but says hosted services and user data were not impacted.
ESET researchers documented a new wave of activity from FrostyNeighbor (a.k.a. Ghostwriter, UNC1151, UAC-0057), the Belarus-aligned group that has been targeting Ukraine, Poland, and Lithuania since 2016. Since March 2026, the group has been sending spear-phishing PDFs impersonating Ukrainian telecom operator Ukrtelecom. The lure server checks the visitor's IP: Ukrainian addresses get a malicious RAR archive that drops a JavaScript version of PicassoLoader, which in turn pulls down a Cobalt Strike Beacon, while everyone else just sees a clean decoy PDF. Operators appear to manually approve which fingerprinted victims actually get the implant.
Symantec's Threat Hunter Team detailed a global cyber-espionage campaign by MuddyWater (a.k.a. Seedworm, Static Kitten, Temp Zagros), an APT linked to Iran's Ministry of Intelligence and Security. The group hit at least nine organizations on four continents in Q1 2026 - including a major unnamed South Korean electronics manufacturer where attackers maintained access from February 20 to 27. They abused signed legitimate binaries fmapp.exe (a Fortemedia audio utility) and sentinelmemoryscanner.exe (a SentinelOne component) to sideload malicious DLLs called fmapp.dll and sentinelagentcore.dll, both carrying the ChromElevator post-exploitation tool that lifts data from Chrome-based browsers. Stolen files were staged through public file-transfer service sendit[.]sh to blend in.
ReliaQuest researchers say initial access broker KongTuke has shifted from web-based ClickFix and FileFix lures to Microsoft Teams social engineering, taking as little as five minutes to gain persistent access. The attacker reaches employees from one of five rotating Microsoft 365 tenants, uses Unicode whitespace tricks to make the display name look like internal IT help desk, then talks the victim through pasting a PowerShell command. That command downloads a ZIP from Dropbox containing a portable WinPython runtime and a Python-based RAT called ModeloRAT. The new ModeloRAT variant adds a five-server C2 pool with automatic failover, self-update, and randomized URL paths, and several major EDR products did not detect it.
Bitdefender researchers documented a China-linked espionage group called FamousSparrow repeatedly compromising an Azerbaijani oil and gas company between late December 2025 and late February 2026. Each time the victim cleaned up, the attackers came back through the same unpatched Microsoft Exchange Server and dropped a new backdoor - first Deed RAT (a ShadowPad relative used by several Chinese groups), then TernDoor. The group overlaps with the Earth Estries cluster, which itself overlaps with Salt Typhoon. This is the first time FamousSparrow has been seen targeting South Caucasus energy infrastructure, a region whose role in supplying gas to Europe grew sharply after Russia's Ukraine transit deal expired.
Socket researchers found more than 150 RubyGems packages doing something the registry was never built to do: smuggling scraped data out of UK council websites. The malicious gems fetch pages from Lambeth, Wandsworth, and Southwark's public meeting portals, bundle the responses into a normal-looking .gem archive, and push it back to RubyGems using a hardcoded API key. The attacker then downloads the data as a public gem version. Whether GemStuffer is registry spam, a worm being tested, or a deliberate trial of package-registry abuse, the mechanics are intentional - and it landed the same week RubyGems froze new account signups over a separate flood of malicious packages.
The Gentlemen, the second most prolific public ransomware operation of 2026 with over 320 listed victims, has had its own internal database leaked. Check Point Research and others obtained the data after a breach of the group's hosting provider 4VPS exposed their Rocket backend. The leak unmasks roughly 9 named operators centered on an administrator known as zeta88 (aka hastalamuerte), who built the RaaS panel in three days using DeepSeek and Qwen AI coding assistants, runs payouts, and joins encryption events personally. Internal chats also confirm chain-victimization: in April the group hit a UK software consultancy and then weaponized stolen client credentials to compromise one of the consultancy's customers in Turkey.
TeamPCP launched its largest supply-chain attack to date on May 11, compromising 170+ npm and PyPI packages with 518 million combined weekly downloads. The attackers chained three GitHub Actions vulnerabilities to publish 401 malicious versions carrying valid SLSA Build Level 3 attestations - cryptographically indistinguishable from legitimate releases. Affected packages include TanStack, Mistral AI (npm and PyPI), UiPath, OpenSearch, and Guardrails AI. The worm installs a persistent gh-token-monitor daemon that triggers 'rm -rf ~/' if tokens get revoked, and includes a probabilistic full-disk-wipe routine for Israeli and Iranian locales.
TeamPCP, the group behind the March Trivy breach and Shai-Hulud npm worm, used credentials stolen in that March attack to publish a backdoored version of Checkmarx's Jenkins AST plugin to the Jenkins Marketplace. This is the third Checkmarx supply-chain hit since late March. The rogue version 2026.5.09 went up on May 9, outside Checkmarx's normal release process - no git tag, no GitHub release. Checkmarx says its GitHub repos are isolated from customer production and no customer data is stored there, but anyone who installed the bad plugin should assume their CI credentials are compromised, rotate them all, and hunt for lateral movement.
TrustStrike Labs