Selected Engineering Work
x402Shield
Verified selected engineering work for Rust-based AI-agent, MCP-tool, and API-payment security.
View caseSubscription & Payment Infrastructure Security
For United States teams, the approved NIST CSF-aligned readiness context keeps Subscription & Payment Infrastructure Security focused on documented priority gaps and written remediation direction. It reviews agreed payment, subscription, webhook, and access-state paths, then documents security and business-logic priorities. The work stays within agreed scope and does not certify compliance, issue approval, or guarantee an outcome.
From $5,900.00 USD
Informational
Final scope, any applicable taxes, third-party costs, and commercial terms are confirmed in a written proposal. Checkout and payment are not available.
How We Deliver
This is a security and logic review of authorised payment and access paths. It does not provide fraud prevention guarantees, processor approval, or compliance certification.
Good fit if
- ✓You have production-facing web or mobile assets that need documented security observations
- ✓You need prioritised findings to support customer, procurement, or governance discussions
- ✓You're preparing for deeper testing, hardening, or compliance readiness work
- ✓You want a written baseline before deciding on next security steps
Not a fit if
- –You need immediate remediation implementation rather than assessment
- –You require 24/7 monitoring, SOC, or MDR services
- –You need certification, compliance approval, or formal audit opinion
- –You expect guaranteed elimination of all security issues
Ideal for
- Teams using payment links, subscriptions, invoices, checkout, or webhook-driven access changes.
- Founders who need confidence that paid access, cancellations, refunds, and failed payments behave as intended.
- Operators preparing to launch or stabilise paid plans without commissioning a broad compliance engagement.
What you'll receive
Payment and subscription flow review notes
Webhook, invoice, cancellation, refund, and access-state observations
Prioritised remediation roadmap
Truth-safe written handover for technical and operational owners
After You Request This Service
When you select a package tier, you submit a request. We review scope in writing before any later commercial step. This page does not take payment, open intake, or start work.
Informational scope prices
Starter
$5,900.00 USD
Informational
Focused review of one checkout, subscription, or payment-link flow.
Request a written proposalMost Popular
Standard
$12,900.00 USD
Informational
Broader review across subscription state, invoices, webhooks, refunds, cancellations, and access changes.
Request a written proposalPremium
$24,900.00 USD
Informational
Expanded review across multiple payment paths, account states, edge cases, and operational handover needs.
Request a written proposalIncluded
- Review of agreed checkout, subscription, invoice, webhook, refund, cancellation, and payment-state paths
- Access-control and paid-entitlement logic review for authorised surfaces
- Business-logic issue identification and prioritised remediation guidance
- Written findings with practical next steps
Excluded
- Fraud prevention guarantees or guaranteed revenue protection
- Payment processor setup as the primary scope
- Compliance certification, PCI certification, or processor underwriting
- Ongoing monitoring, chargeback operations, or managed fraud response
Available Add-ons
- +Implementation support for agreed remediation items
- +Expanded review of additional payment products or markets
- +Follow-up validation after fixes are applied
How it works
1
Scope & Access Confirmation
Confirm authorised payment flows, test accounts, system boundaries, and operational questions before review begins.
2
Flow & State Review
Review checkout, subscription, invoice, webhook, refund, cancellation, access-control, and payment-state paths against the agreed scope.
3
Findings & Prioritisation
Document observed risks, ambiguity, and logic gaps with practical remediation priorities.
4
Handover
Provide a written handover that separates confirmed findings from recommendations and scope boundaries.
Timeline: Confirmed during intake based on scope and package tier. Typical delivery timeframes provided after intake completion.
Custom Scope Available
For regulated payment infrastructure, certification work, or broad fraud operations, request a separate scope. This service stays limited to authorised security and business-logic review.
Discuss Custom ScopeRepresentative deliverable
Example of the written artefact produced after a scoped review.
Subscription businessPayment logic reviewScoped sprintFounder, developer, operations owner
Challenge
The team needed to understand whether paid access, failed payment states, cancellations, refunds, and webhook events could create unintended access or operational gaps.
Scope applied
- Reviewed authorised payment and access-state paths
- Mapped payment states to user access outcomes
- Prioritised remediation by customer and operational impact
Result
The buyer received a written findings pack with practical remediation sequencing and clear boundaries around what was and was not reviewed.
Deliverable preview
Payment-state security review pack
- Scope and assumptions
- Flow observations
- Access-state findings
- Prioritised remediation roadmap
Example finding
A cancelled subscription path did not consistently remove access until a delayed webhook event completed.
Delivered as a written report with prioritised action items.
Security File context
How this deliverable fits into the Security File
This representative deliverable shows the kind of evidence, priorities and follow-through notes that can sit inside a practical BilgeQor Security File after handoff.
The Security File is a decision aid, not a certification, compliance verdict, guarantee of perfect security, or per-company loss estimate.
Truth-safe noteExample only. Outcomes depend on authorised scope, access, implementation quality, and buyer follow-through.
Frequently Asked Questions
Related evidence
Relevant Engineering work
Selected public case records related directly to this service scope. Each record keeps its attribution and disclosure boundary visible.
Ready to get started?
Choose a package tier or talk to us about custom scope