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Threat actors have weaponized a now-patched security flaw in Zimbra Collaboration Suite (ZCS) to deploy web shells and access mailbox data, according to findings from the Microsoft Security Research team. The attack exploits CVE-2026-73570 (CVSS score: 8.9), an unauthenticated operating system command injection flaw that can lead to remote code execution when Simple Network Management Protocol (SNMP) notifications are enabled and the optional zimbra-snmp package is installed. Exploitation of CVE-2026-73570 can be triggered by a specially crafted SMTP request (i.e., email against exposed Zimbra servers without requiring authentication or user interaction. The vulnerability was patched by Zimbra in July 2026 with the release of version 10.1.20. "Following successful exploitation, observed activity included deployment of JSP web shells and reverse shells, privilege escalation, persistent remote-access tooling, and memory-backed execution," the tech giant said . "Thr...

Microsoft has warned of phishing campaigns distributing an installer for the MSP360 Remote Monitoring and Management (RMM) software under the guise of meeting invitations, PDF-themed lures, software update prompts, and other social-engineering content. "Once executed, the legitimate MSP360 installer, distributed under a deceptive file name established remote management access on affected devices and enabled threat actors to gain an initial foothold using trusted administrative software," the Microsoft Security Research team said . The initial foothold is then used to download and install a ConnectWise ScreenConnect client, offering threat actors a redundant remote-access channel to compromised endpoints. The access is then abused to deliver additional tools and carry out information collection and credential-access operations. The activity has not been attributed to any known threat actor or group. The multi-stage intrusion chain, which the Windows maker detected in Ju...

Attackers are exploiting a new critical zero-day flaw in Cisco Catalyst SD-WAN Manager, the system companies use to manage their Cisco SD-WAN networks, Cisco said in an  advisory  on September 30. The flaw, CVE-2026-76504 , could allow a remote attacker with no login access to use the Manager's API as the admin user. Fixed releases are available, and there is no workaround. It carries a CVSS score of 9.8 out of 10. It sits in the part of the Manager's API that handles login sessions. The Manager mishandles URI encoding in an HTTP request. A crafted request can therefore bypass an authentication rule intended to restrict access to a single API endpoint. The attacker needs no credentials, only the ability to send that request to the Manager's API. Managers exposed to the internet are at risk of compromise, according to Cisco. By default, the admin user holds the netadmin role, which is allowed to perform all operations on the device. Cisco said its Product Security I...

Threat actors are abusing ChatGPT Custom GPTs to disguise them as legitimate product offerings and direct unsuspecting victims to malicious sites that employ ClickFix lures to deliver malware. Huntress, which observed the activity in late September 2026, said it marks the abuse of yet another feature in trusted artificial intelligence (AI) platforms. Prior campaigns have weaponized shared conversations with AI chatbots and malicious Claude Artifacts to distribute stealer malware and remote access trojans (RATs). Custom GPTs refer to a personalized version of ChatGPT that, as the name implies, allows users to define custom instructions, upload reference files, and enable specific skills to handle unique tasks without any coding. They are hosted on the legitimate ChatGPT website with the Custom GPT name at the top. "In the incidents we saw, victims interacted with an attacker-created Custom GPT, which was programmed to respond to their prompts with a message that includ...

Given that the browser is where business apps are accessed and used, it makes sense that attacks are happening there too. Most breaches today begin in a browser session. Often, they never leave it, with the entire attack chain from initial access to exfiltration playing out in the browser. Here are the six most dangerous techniques that should be on every security team's radar in 2026. 1. Phishing for credentials and sessions Modern phishing kits don't just steal passwords — they intercept live sessions. Reverse-proxy adversary-in-the-middle (AiTM) kits like Tycoon2FA, Sneaky2FA, and Evilginx relay credentials and session tokens in real time, bypassing most forms of MFA. These kits are sold as turnkey Phishing-as-a-Service platforms with anti-bot protection, dynamic lure generation, and automated session replay — reducing the barrier to sophisticated phishing to effectively zero. At the same time, phishing delivery has moved well beyond email — attackers deliver link...

AI coding agents asked to share screenshots of code changes for review have put internal company images in public GitHub repositories, security company Glow said. Its researchers found more than 13,000 internal images from developers at over 300 organizations, including customer billing records and screens of features not yet released. In most cases, they sat under developers' personal accounts, where anyone could download them but company security teams did not see them. The affected organizations include one of the world's largest tech companies, a leading AI lab, a major enterprise software provider, and a Fortune 500 travel company. Glow began contacting them on September 9,  published its findings  on September 29, and says others are likely affected too. In one case, a developer at a manufacturer with more than 100,000 employees asked an agent to check a fix to an internal billing screen. The agent created a public repository in the developer's personal GitHub ...

ANY.RUN researchers traced a US-focused CSuite phishing campaign across 351 sandbox analyses, with 51% of submissions coming from the United States. Technology, manufacturing, government, and consulting organizations showed the highest exposure. By combining Microsoft 365 session theft with remote-access tool deployment, CSuite can turn a phishing incident into broader account compromise, fraud, and persistent access to business systems. CSuite Phishing Leads to Both Account and Endpoint Access CSuite attack chain exposed by ANY.RUN researchers CSuite starts with familiar business lures built around Adobe, DocuSign, Zoom, Google Meet, Dropbox, and Microsoft 365. A forged DocuSign envelope in the name of a law firm analyzed inside ANY.RUN’s Interactive Sandbox From there, the operation can move in two directions. One path delivers installers, archives, or lightweight BAT/VBS droppers that install legitimate management tools such as ScreenConnect or Action1, giving attackers...

Unknown threat actors have been observed exploiting a newly patched security flaw in Citrix NetScaler ADC and NetScaler Gateway appliances to target organizations in North America and Europe. The activity, observed by Mandiant Consulting and Google Threat Intelligence Group (GTIG) in September 2026, has targeted government, financial services, technology, education, and legal and professional services sectors. In a post shared on LinkedIn, Charles Carmakal, chief technology officer at Mandiant Consulting, said the targeted intrusions have impacted dozens of organizations, warning of "broad and opportunistic exploitation of CVE-2026-88772 and CVE-2026-88771 by a variety of threat actors in the near term." "Exploitation of CVE-2026-88772 bypasses authentication and triggers an unhandled termination of the NetScaler Packet Processing Engine (NSPPE) to establish initial root-level access," the tech giant said . The attacks have been observed weaponizing the f...

A High-severity OpenSSL flaw can leak heap memory to the other side of a DTLS connection or crash the program,  OpenSSL said  on September 29 as it released fixes. DTLS , the TLS variant used for UDP traffic, resends a handshake message if no reply arrives before the timer expires. The leak or crash can happen when such a resend starts while a larger handshake message is stuck part-way through being sent. The flaw, tracked as CVE-2026-84782, is fixed in  OpenSSL 4.0.3, 3.6.5, 3.5.9 and 3.4.8 . Fixed versions for the older 3.0, 1.1.1 and 1.0.2 branches go only to customers who pay for OpenSSL's premium support. OpenSSL 3.0  stopped getting public security fixes  on September 7. OpenSSL has not said whether an attacker can cause a resend while a message is stuck, nor has it reported any attacks exploiting the flaw. DTLS is used, for example, to protect WebRTC data channels and to set up encryption keys for internet calls. Software is exposed to this fla...

Cybersecurity researchers have disclosed technical details of a recently patched critical security flaw in Citrix NetScaler ADC and Gateway that has come under active exploitation in the wild. The vulnerability, tracked as CVE-2026-88772 (CVSS score: 9.5), has been described as a memory overflow bug in the Datagram Transport Layer Security (DTLS) protocol handling that's rooted in the NetScaler Packet Processing Engine (NSPPE). "Citrix NetScaler ADC and NetScaler Gateway contain an improper restriction of operations within the bounds of a memory buffer vulnerability that could allow for remote code execution or denial-of-service," the U.S. Cybersecurity and Infrastructure Security Agency (CISA) said . The issue, per watchTowr , is that NetScaler implicitly trusts the declared fragment size in the DTLS handshake header's fragment_length field (i.e., 1 byte), while the header simultaneously claims that the complete message, as denoted by the length field, is 120...

An attacker used stolen passwords of staff at France's tax administration to take tax data on hundreds of thousands of taxpayers and businesses in June and July. Neither the tax administration nor France's national cybersecurity agency saw the data leave. The attack was not sophisticated, the agency, ANSSI, says in a  report  (in French) published on Tuesday: it worked because of weak login protection, poorly separated networks and gaps in monitoring. The tax administration, known as the DGFIP, runs France's tax website, impots.gouv.fr. The data came from E-Contact, the tool taxpayers use to message the tax administration. The stolen data covers  a little over 350,000 individuals  and  a little over 250,000 businesses , the DGFIP says. Taxpayers' own online accounts and passwords were not compromised. For individuals, the data that may have been viewed or copied includes their tax ID, contact details, family situation, reference taxable income and tax...

A group of academics from VUSec and Scuola Superiore Sant'Anna have disclosed details of a new Spectre CPU vulnerability variant that affects Just-In-Time ( JIT ) engines present in web browsers, language runtimes, and the operating system kernel, across multiple CPU vendors. The new Spectre v2 variant has been codenamed Branch Target Reuse (BTR) . "The key insight is that, while modern CPUs restore architectural code coherence after self-modification, they do not necessarily invalidate stale indirect branch prediction entries (i.e., branch targets)," researchers Sander Wiebing, Yuhui Zhu, Alessandro Biondi, and Cristiano Giuffrida said in an accompanying paper. "In JIT engines, these stale targets can outlive the original code and later be reused when the code cache is repopulated, yielding a transient execute-after-free primitive. This allows attackers to hijack transient control flow to newly generated code at obsolete offsets, bypassing software hardening...

Russian state hackers known as Star Blizzard have been using fake event invitations to trick people into installing a backdoor on their Windows computers, according to Microsoft. The campaigns, aimed at people and organizations tied to Ukraine, have affected more than 100 organizations since January, mostly in the U.S. and U.K. At least one computer was infected, but the number of breached organizations has not been disclosed. Security agencies in the U.S., U.K., Australia, Canada and New Zealand  said in December 2023  that Star Blizzard almost certainly works under Center 18 of Russia's Federal Security Service (FSB). The group has long stolen email passwords by posing as people its targets know. By 2023, it had already used  fake conference and event invitations  as bait, often exchanging messages with a target before sending a malicious link. Microsoft counted at least 13 larger campaigns this year, each with tens to hundreds of emails, on top of ...

Kiteworks on Monday said it worked with federal intelligence authorities over the weekend as it identified and addressed a critical security vulnerability during the scheduled precautionary shutdown . "During the shutdown, this activity led to the discovery of a previously unknown critical vulnerability confined to a capability that is enabled for less than 1% of the customer base," the company said in a statement. "Kiteworks developed and deployed a fix during the window, [and] applied an additional protective layer across all environments." There is no evidence that the vulnerability has ever been exploited in a malicious context. Other Kiteworks products are not affected by the flaw. The development comes days after Kiteworks, previously Accellion, urged customers to take their systems offline for a period of nine hours, in addition to shutting down environments it hosts on behalf of customers, after receiving intelligence about a potential imminent cybe...

Cybersecurity researchers have identified a cluster of 101 npm packages that are used to trap developers into a WhatsApp group subscriber campaign dubbed PhantomSub . "The malicious packages abuse the 'Baileys' WhatsApp open source project to add the victims to groups without their consent," OX Security researchers Nir Zadok, Moshe Siman Tov Bustan, and Vitalii Chepurko said in a technical write-up published Monday. These packages have been collectively downloaded 490,000 times, out of which 116,000 occurred in the last 30 days. The names of some of the packages are below - ourin-baileys @nexustechpro/baileys @badzz88/baileys @ostyado/baileys levvleys @vanzxy/baileys @yudzxml/baileys @chatunity/baileys @kelvdra/baileys neuralwhatsapp lilys-baileys @fyxzpediaa/baileys noxleyss @xrelly-stack/bails alipclutch-baileys kurobails eliteprotech-baileys @xayz/baileys chromestaff-baileys @sanzoffc/baileys @s...

Dutch authorities have confirmed that they arrested a 24-year-old man from Amsterdam in connection with the ShinyHunters group. "It is true that this month a 24-year-old man from Amsterdam was arrested in an investigation into the hacker group ShinyHunters," the Politie Landelijke Opsporing en Interventies said in an X post Monday. Police said the individual is expected to appear before the Rotterdam District Court on September 29, 2026. Although law enforcement officials did not disclose any additional details, independent security journalist Brian Krebs and DataBreaches.Net identified the arrested man as Pepijn van der Stap (aka Umbreon), who was previously apprehended in 2023 for his role in a series of data thefts and extortions. Per DataBreaches.Net, van der Stap was arrested on September 15, 2026. In 2023, it emerged that the individual worked at cybersecurity company Hadrian and volunteered at the Dutch Institute for Vulnerability Disclosure (DIVD). ...