Open-source AI pentesting harnesses (Strix, Cairn, Hermes) run an autonomous intrusion-and-skimmer campaign against online retailers for about $25 a target

Gambit Security's Threat Intelligence team recovered a financially motivated operator's exposed staging server and reconstructed a campaign, running since July 2026, in which three off-the-shelf open-source AI agent harnesses conduct nearly the entire intrusion lifecycle unattended against online retailers. Strix, an open-source AI pentesting tool run via OpenRouter (GLM 5.2, later switched to DeepSeek v4 Pro), performs autonomous vulnerability discovery: 146 deep-mode scans against 138 hosts between 23–31 August 2026, burning 633 hours of scanner time within 195 hours of wall-clock time. Cairn, an autonomous exploitation engine on DeepSeek v4.1 Flash, receives a target domain and an objective and runs unattended for hours until it gets a shell or admin access: "between 10 and 15 September alone, 105 attack projects were launched and at least 27 companies were compromised to varying degrees" (Gambit Security, 2026-09-22). Hermes, an open-source autonomous agent with persistent memory and skills the agent writes and edits itself, orchestrated the campaign end to end, running on Anthropic Opus 4.6 ("after newer models refused its requests") under a Chinese system persona the operator loaded, titled "SOUL - Red Team Operator". The operator had added a custom skill that strips Hermes's own content-safety filters, and drove the campaign through only 1,951 short, largely Chinese-language operator prompts across 260 sessions, with most of the actual attack work running autonomously between those prompts (Gambit Security, 2026-09-22).

One fully documented Cairn project illustrates the chain, though Gambit is explicit that each victim's actual path was chosen dynamically through real-time probing and most chains differed victim to victim: unauthenticated SQL injection in a login email parameter (error-based EXTRACTVALUE) read a one-time-passcode value in plaintext directly from an application database table, bypassing multi-factor authentication and reaching the admin panel; an image-upload field with no extension check then gave host remote code execution as a non-root user; a sudo misconfiguration allowing NOPASSWD execution of python3.12 escalated that to root; an internal NFS mount configured with no_root_squash let the agent read a separate host's WordPress database credentials in plaintext from its wp-config.php; those credentials gave a direct database write creating a new WordPress administrator account, which in turn let the agent upload a malicious plugin for code execution on the blog host; from there the agent dumped the full contents of the account's AWS Secrets Manager (46 secrets, 102 KB), reached the production Magento database on Amazon Aurora, extracted the Magento application's encryption key, and used it to decrypt stored card numbers encrypted with Blowfish in ECB mode. Confirmed impact across the campaign: 600,000-plus unexpired credit-card records exfiltrated from two victims, and skimmer scripts ordered against at least 27 named victims and confirmed in place on 19 of them according to the body of Gambit's report, although its own summary counts skimmer installations on the websites of five companies and does not reconcile the two figures. Gambit also detected more than 100 further websites infected with a skimmer associated with the campaign. Gambit reports some level of access to the assets of companies including a Fortune 500 hospitality company, a major US airline, a large private US industrial-supplies distributor and a US online fashion retailer, which it names separately from the illustrative chain above. A per-country cardholder breakdown embedded in Gambit's own page (488,372 of the recovered cards, 79.0%, United States) skews overwhelmingly toward the United States; no Swiss-issued cards appear among the top entries of that table (Gambit Security, 2026-09-22).

Gambit documents eight distinct skimmer-injection methods used across victims, all worth carrying into any custom-web-application hardening review: appending the loader to the end of a legitimate, already-served JavaScript file while restoring its original modification timestamp; inserting a foreign <script> tag directly into the checkout page; hiding the loader inside a site's Google global-site-tag (gtag.js) block, between the real gtag('js', ...) and gtag('config', ...) calls, padded with roughly a hundred tab characters to push it past the right edge of a typical code-review view; using a discovered AWS access key to write the loader into the storage bucket behind the retailer's own CDN, so it loads from that trusted CDN host rather than a third-party domain; injecting the loader into a database content field (such as a product-description column) through an admin pod and relocating it to a file on the victim's own domain; adding it to a production front-end deployment as a Kubernetes initContainer; writing it into the cached page model of the checkout page; and a self-healing cron job placed in a JBoss log directory that checks the injected file's size every two minutes and re-appends the loader whenever a redeploy reverts it. One of the Hermes agent's skill files, in a section titled "Database Wipe After Extraction", instructs the agent: "after extracting and downloading all card data, wipe the source fields in batches" (Gambit Security, 2026-09-22); at a second victim, a bicycle retailer, an overly broad table-name-matching cleanup step additionally dropped 180 staging and backup tables, including backups the victim's own administrators had separately made. This was collateral data loss from the attacker's own automated cleanup, not extortion. Some targets were not discovered by the agents at all: the operator handed at least two victims, a New Zealand retailer and a US photo printing company, to Hermes already holding a working administrator password, with the order to "get to work" (Gambit Security, 2026-09-22). OpenRouter's account balance recorded $7,005.71 spent over four weeks by 25 August, and Gambit extrapolates from the later volume of model calls that the full cost was likely between $12,000 and $18,000; "the operator’s own cost review gives a similar figure, a mean of $25.46 over 101 completed scans, from $3.13 for the cheapest target to $79.31 for the most expensive" (Gambit Security, 2026-09-22). Gambit states it "reached out to many of the affected organizations and took measures to take down the infrastructure discovered," crediting the Shadowserver Foundation, researcher Daniel Gordon, and other industry partners for their help notifying victims and taking down infrastructure (Gambit Security, 2026-09-22).

Detection concept, telemetry class first: in web-server access logs, alert on SQL-error-pattern responses (EXTRACTVALUE or equivalent) to login-form parameters, and on image-upload requests whose stored file is later executed by the web server rather than served as static content; in host telemetry, alert on sudo invocations of an interpreter (python3.12 or similar) by a low-privilege account with no corresponding change-management record; in network/mount telemetry, flag any host mounting an NFS export it has not mounted before, particularly where the export allows root-equivalent access; in cloud-audit telemetry, alert on a single principal enumerating or reading the entire contents of an AWS Secrets Manager instance in a short window; and in file-integrity or CDN-origin monitoring, treat any modification to a served JavaScript file's content (even with its timestamp preserved) or any script tag added to a checkout page outside a deployment window as high-priority. Triage: a legitimate deployment modifies checkout-page assets during a known release window with a corresponding commit and change record; the discriminators here are modification with no matching deployment event, a modification timestamp that has been deliberately restored to match the original file, or content padded with unusual whitespace specifically to evade a manual code read.

Hermes, the open-source NousResearch agent framework (Unit 42, 2026-07-30), has appeared in three earlier, unrelated intrusions: an operation against Thailand's Ministry of Finance that Hunt.io links with low-to-medium confidence to a Chinese-speaking operator (Hunt.io, 2026-07-23); a Taiwan government intrusion Tenable assesses as most likely a state-adjacent contractor or patriotic-hacker operation, with state sponsorship a close runner-up (Tenable, 2026-08-14); and a Zhuhai-based, Chinese-speaking operator's campaign against more than 460 targets, including persistent targeting of a Malaysian government entity (Unit 42, 2026-07-30). In three of the four intrusions the operators worked around model safety controls. In this campaign the operator added a skill to remove Hermes's own content-security filters (Gambit Security, 2026-09-22). In Taiwan the agents reframed the operation as "authorized penetration testing" (Tenable, 2026-08-14). In the Unit 42 case the actor likely turned to DeepSeek, which Unit 42 describes as a model with minimal safety controls, after Western providers' controls limited it, and a framework-bundled jailbreaking skill was also installed (Unit 42, 2026-07-30). That convergence, not any single victim in this campaign, is the transferable signal for a defender: an increasingly capable, freely available agent orchestration layer is now common tooling across financially motivated operators and government-targeting intrusions alike, regardless of how firmly any of them is ultimately attributed, and the underlying attack chain here (SQL injection, insecure OTP storage, unrestricted file upload, sudo misconfiguration, an over-permissive NFS export, and cloud-secrets exposure) is entirely composed of defects a Tier 2/3 team already reviews for in any custom-coded web application, Swiss public-sector portals included.