Huntress observed a 155x increase in password spraying attacks in H1 2026, including a campaign that generated more than 81 million login attempts in two weeks. The attacks exploited legacy authentication and gaps in MFA policies that left some login flows unprotected.
Microsoft has resolved a bug that caused Windows Defender to crash after a recent security update, resulting in 0xc0000005 access violation errors on some affected systems. Microsoft Defender is a security software designed to provide real-time protection against malware, viruses, ransomware, and spyware on Windows, macOS, Linux, Android, and iOS devices. According to reports on social media and Microsoft's support site, users began seeing "Threat service has stopped. Restart it now" error messages on Windows 10 and Windows 11 devices starting Tuesday afternoon, prompting some affected customers to reinstall the operating system. "Beginning this morning, quick or full scans are failing, and will occasionally fail to the point where the Defender service needs to be restarted," one Windows system admin said.
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) warned that hackers are exploiting a critical-severity remote code execution (RCE) flaw in the Windows Internet Key Exchange (IKE) Service Extensions component. Also known as MS-IKEE, this is a set of additional capabilities Microsoft added to the IKE Protocol, including authentication via cryptographically generated addresses (CGAs), denial-of-service protection, and easier interoperability with non-Internet Protocol Security (IPsec)–capable peers. Tracked as CVE-2026-33824, this RCE vulnerability impacts all supported Windows 10, Windows 11, and Windows Server releases, and it allows attackers without privileges to gain code execution by sending maliciously crafted packets to unpatched Windows systems through UDP ports 500 or 4500.
Microsoft tracked over 30 MacSync Stealer domains by focusing on behavioral patterns, revealing a campaign targeting passwords, keys, wallets and other data. Domain blocking is a losing game when the thing you’re blocking can register a new domain faster than you can add it to a list. That’s the exact problem Microsoft Defender Experts ran into while tracking MacSync Stealer, a macOS-focused information stealer that RST Cloud first flagged for swapping out its command-and-control infrastructure almost immediately after getting publicly outed. Microsoft detailed how its experts stopped chasing individual domains and started tracking the behaviors that stayed constant underneath them. Instead of tracking individual domains, Microsoft looked at recurring request patterns, HTTP headers and other behaviors. This allowed its researchers to link more than 30 domains to the same campaign and determine that the infrastructure was doing more than just sending commands to infected Macs. It was also being used to collect, stage and exfiltrate stolen data. “MacSync Stealer is a macOS-focused information stealer that relies on changing infrastructure to deliver payloads, communicate with compromised devices, and exfiltrate data. Earlier reporting by RST Cloud identified the threat through a limited set of domains and documented rapid command-and-control (C2) replacement after public disclosure.” reads the report published by Microsoft. “Microsoft Defender Experts expanded that view by correlating recurring endpoints and network behaviors across the activity. This behavior-led approach connected more than 30 domains and showed that the infrastructure supported more than C2 communication, extending into active collection, staging, and exfiltration.” The infection chain starts with a trick rather than an exploit. Victims get social-engineered through a technique known as ClickFix, tricked into pasting or running commands directly in macOS Terminal, and once that shell session fires, curl pulls down attacker-controlled payload content from a path formatted as /curl/[token]. Then, native macOS tools decode and unpack the payload, and an AppleScript-driven layer takes over, blending Unix commands like sh, cp, rm, and killall with osascript calls that make the whole chain look more like ordinary system scripting than malware. Once active, the stealer focuses on valuable data. The malicious code looks for macOS Keychain data, saved browser passwords and cookies, SSH keys, AWS credentials, Kubernetes configurations and files in common user folders. It also searches for Ledger and Trezor wallet data, showing that the malware targets users with valuable credentials and assets rather than simply collecting random browser history. What actually confirms exfiltration, rather than just suspicious traffic, is the upload mechanism itself. Collected data gets staged under temporary paths, compressed into an archive, split into chunks, and pushed out through HTTP PUT requests carrying parameters like upload_id, chunk_index, and total_chunks. “The staged archive was uploaded through rotating infrastructure using curl and HTTP PUT requests. Observed requests included –data-binary, API-key headers, macOS User-Agent string, upload_id values, chunk_index values, and total_chunks parameters.” states Microsoft. “These upload traits confirmed active data exfiltration and provided durable hunting pivots even when domains rotated. “ The researchers pointed out that the exfiltration method stays recognizable even when the destination keeps changing. RST Cloud’s follow-up work backs up how consistent this infrastructure actually is under the surface. Using the same recurring URI patterns, RST Cloud surfaced eleven additional candidate domains and found a static API-key value shared across four confirmed command-and-control domains, even while the build token attached to each deployment kept rotating. A shared static key sitting inside otherwise rotating infrastructure is exactly the kind of detail that makes automated evasion look less impressive up close. The attack wraps up with cleanup, deleting temporary archives, staging folders, and lock files after the upload completes. Microsoft notes this reduces what’s left sitting on disk, but it doesn’t erase the behavioral sequence itself. “After exfiltration, the malware removed temporary archives, staging folders, lock files, and other artifacts. Although this cleanup reduced on-disk evidence, the sequence of archive creation, chunked upload, and deletion can still provide a useful behavioral correlation for defenders.” concludes Microsoft. For anyone defending Mac fleets, the practical takeaway here isn’t a list of domains to block, since that list will be stale within days. It’s building detection around the recurring shape of the attack itself: shell sessions spawning curl with those specific flag patterns, osascript chaining rapidly into network activity, and archives appearing under /tmp/sync* right before outbound PUT traffic starts. Chase the pattern, not the address, because the address was never going to sit still long enough to matter. Follow me on Twitter: @securityaffairs and Facebook and Mastodon Pierluigi Paganini (SecurityAffairs – hacking, malware)
The Cybersecurity and Infrastructure Security Agency (CISA) said Tuesday that the Medusa ransomware gang has breached more than 500 critical infrastructure organizations in the United States since June 2021. This was revealed in a joint advisory in coordination with the Department of Health and Human Services (HHS) and the Federal Bureau of Investigation (FBI). "As of April 2026, Medusa actors have impacted more than 500 victims across multiple critical infrastructure sectors, including Healthcare and Public Health, Defense Industrial Base, Critical Manufacturing, Government Services and Facilities, Information Technology, and Financial Services," they said. "Other victims include organizations in the medical, education, legal, insurance, technology, and manufacturing industries." This is an update to a joint report published in March 2025, which said the Medusa ransomware operation had impacted an estimated over 300 critical infrastructure organizations.
U.S. Cybersecurity and Infrastructure Security Agency (CISA) adds Apple macOS, Microsoft SharePoint, Broadcom VMware vCenter, and Microsoft IKE flaws to its Known Exploited Vulnerabilities catalog. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added the following vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog: CVE-2026-33824 (CVSS score: 9.8) – Microsoft Internet Key Exchange (IKE) Service Extensions Double Free Vulnerability CVE-2026-55040 (CVSS score: 9.1) Microsoft SharePoint Weak Authentication Vulnerability CVE-2026-59310 (CVSS score: 9.8) Broadcom VMware vCenter Path Traversal Vulnerability CVE-2026-65400 Apple macOS Improper Authentication Vulnerability CVE-2026-33824 is a Windows Internet Key Exchange (IKE) Service Extensions Remote Code Execution Vulnerability. This critical flaw in Windows IKE service extensions could allow remote attackers to execute code on affected systems. Systems with IKE enabled are at risk, though blocking UDP ports 500 and 4500 can reduce exposure from external threats. However, internal attackers may still exploit it for lateral movement, so rapid patching is strongly recommended. CVE-2026-55040 is a critical SharePoint authentication bypass. An unauthenticated attacker can exploit weaknesses in JWT validation to forge tokens and impersonate any SharePoint user, including administrators. “A critical authentication bypass vulnerability exists in SharePoint Server Subscription Edition’s JWT token validation pipeline. The root cause is a chain of four distinct weaknesses that, when combined, allow an unauthenticated remote attacker to forge a valid JWT and impersonate any SharePoint site user.” wrote Rapid7. The exploit chain works by sending a JWT with “alg: none” in the outer header so no signature is required, using SharePoint’s own STS certificate thumbprint to resolve a signing key without verification, and then passing a non-empty but never-verified signature like “AAAA.” The result is a fully forged token that SharePoint accepts as legitimate. Defused researchers observed attackers using the Rapid7 POC for CVE-2026-55040 against our SharePoint their honeypots. CVE-2026-59310 flaw is a Path Traversal Vulnerability that allows an attacker with network access to execute arbitrary code. “VMware vCenter contains a directory traversal vulnerability in the Syslog server. Broadcom has evaluated the severity of this issue to be in the Critical severity range with a maximum CVSSv3 base score of 9.8.”states the advisory.”A malicious actor with network access to vCenter may exploit this issue to execute arbitrary code.” CVE-2026-65400 is an Improper Authentication Vulnerability that sits in macOS’s built-in Screen Sharing feature, the remote desktop tool baked into every Mac.On August 15, 2026, the Dutch National Cyber Security Centre confirmed active exploitation of a critical macOS authentication flaw, less than two weeks after Apple shipped the fix. Apple’s fix improved how the system manages authentication state, closing a gap that let attackers on the network authenticate to Screen Sharing without valid credentials at all. Apple patched this issue with the release of macOS Tahoe 26.6.1, macOS Sequoia 15.7.9, and macOS Sonoma 14.8.9, crediting researcher Alfredo Pesoli (@__rev) at Bynario Atlas (bynar.io) for the discovery. “An attacker on the network may be able to authenticate to Screen Sharing without valid credentials” reads the advisory. According to Binding Operational Directive (BOD) 22-01: Reducing the Significant Risk of Known Exploited Vulnerabilities, FCEB agencies have to address the identified vulnerabilities by the due date to protect their networks against attacks exploiting the flaws in the catalog. Experts also recommend that private organizations review the Catalog and address the vulnerabilities in their infrastructure. CISA orders federal agencies to fix the flaws by August 21, 2026 Follow me on Twitter: @securityaffairs and Facebook and Mastodon Pierluigi Paganini (SecurityAffairs – hacking, CISA)
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Tuesday added four critical vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog, stating they are being exploited in the wild. The shortcomings added to the KEV catalog are listed below - CVE-2026-65400 (CVSS score: 9.8) - An improper authentication vulnerability impacting Apple macOS that could allow an
Microsoft Defender Experts have linked more than 30 web domains to MacSync Stealer, a macOS-focused information stealer, after correlating recurring endpoint and network behaviors across changing infrastructure, tracing the malware from payload retrieval through data collection, staging, and exfiltration. The tech giant said it required multiple endpoint and network behaviors to align before
We provide guidance for preparing for and mitigating large-scale credential attacks, focusing on recent campaigns targeting security vendors' devices. The post Threat Brief: Mitigating Large-Scale Credential Attacks (Updated August 18) appeared first on Unit 42.
A Heights Finance breach exposed personal and financial data of over 1.2 million people after hackers compromised a third-party cloud platform. Heights Finance is a U.S. consumer finance company that provides personal loans and related lending services, mainly to customers who may have limited access to traditional bank credit. It is part of Heights Finance Holdings Co. Heights Finance Holdings is notifying more than 1.2 million people that on May 7, 2026, Heights Finance discovered unauthorized access to a third-party cloud platform storing customer data. The company launched an investigation with external cybersecurity experts and notified federal law enforcement. “On May 7, 2026, Heights discovered that an unauthorized actor gained access to a cloud-based platform hosted by a third party that we use to store certain customer data. This activity was limited to the cloud-based platform only—it did not affect any of our loan management systems or other computer systems or networks. We immediately activated our incident response protocols, brought in outside cybersecurity specialists to investigate, and reported the incident to federal law enforcement.” reads the notice of data breach. “We have since confirmed that the cloud-based platform is secure and that there is no ongoing security threat. Our operations were not impacted by this incident and have continued safely and securely.” Heights said its internal systems and operations were not affected, the platform has been secured, and there is no ongoing threat. The compromised customer information included contact details, financial and bank account data, government IDs and dates of birth. The affected data varies by person and may involve Heights Finance customers, loan applicants, people who inquired about its products, or former borrowers of Curo Management and related brands. Heights Finance is offering affected individuals 24 months of free credit monitoring and identity protection. The company said dark web monitoring has found no evidence that the stolen data has been published. No threat actor has claimed responsibility, and no known ransomware or extortion group has been linked to the breach so far. Follow me on Twitter: @securityaffairs and Facebook and Mastodon Pierluigi Paganini (SecurityAffairs – hacking, Heights Finance)
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