A security-testing guide for ASP.NET applications, Microsoft’s web framework, covering issues such as ViewState, leaked machine keys, exposed diagnostic pages and unsafe deserialization.

It is for assessing ASP.NET Web Forms, WCF services, CMS installations and sites using Telerik or similar ASP.NET components.

It helps testers focus on framework-specific weaknesses that may be missed during a general web security review.

hunt-aspnet — Skill for Claude Code and Codex by uphiago

About the project

Recon Skills is a pack of security-testing skills covering reconnaissance, web applications, APIs, authentication, vulnerability validation, cloud infrastructure, and reporting. Security professionals use it for authorized assessments of systems they own or have written permission to test. The catalogue entries are individual skills from the pack.

uphiago/recon-skills · 1,254 stars · on GitHub · hiago.sh

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add uphiago/recon-skills --skill hunt-aspnet

Clone the repo

git clone --depth 1 https://github.com/uphiago/recon-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-aspnet/github.svg)](https://agentmods.dev/skills/uphiago/recon-skills/hunt-aspnet)

Your own site

<a href="https://agentmods.dev/skills/uphiago/recon-skills/hunt-aspnet"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-aspnet/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/uphiago/recon-skills/hunt-aspnet"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-aspnet.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 98 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 5,670 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 3 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

high YARA Match · line 3
YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).

Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.
medium Data Exfiltration · line 128
Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
medium Tool Misuse · line 140
Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.

Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00098	$0.05670
Opus 5	$0.00049	$0.02835
Sonnet 5	$0.00020	$0.01134
Haiku 4.5	$0.00010	$0.00567

Measured 7d ago against content hash 3fac1d822757, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

hunt-aspnet scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl --max-time 30 --connect-timeout 10 -sk -X POST "https://target.example/page.aspx" \

redteam/hunt-aspnet/SKILL.md · 322 lines

How it starts

The opening of the file, as written. The whole thing — 322 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crown Jewel Targets

ASP.NET deserialization bugs pay among the highest amounts in bug bounty when they reach RCE. Even when patched, the disclosure-tier findings (signed-only ViewState, dual-parser differential, request-validator quirks) reliably pay Low-Medium.

Highest-value targets:

SharePoint farms (any version — 2013/2016/2019/SE) — sign-only ViewState + permissive ToolPane.aspx + anonymous FormDigest creates the CVE-2025-53770 ToolShell precondition chain
Telerik UI for ASP.NET AJAX — Telerik.Web.UI.WebResource.axd is a documented RCE sink when keys leak (CVE-2017-11317, CVE-2017-11357, CVE-2019-18935)
Classic ASP.NET Webforms enterprise apps — banking portals, dealer portals, HR systems left on .NET Framework 4.x
WCF services (*.svc?WSDL) — often forgotten admin endpoints with looser auth than the main app
Sitecore CMS — ViewState + Sitecore-specific deserialization chains (CVE-2021-42237)
DotNetNuke (DNN) — historic ViewState RCE chains
Umbraco CMS — ViewState + custom deserialization sinks

Asset types that pay most: internet-reachable ASP.NET Webforms apps > WCF admin services > Telerik-integrated sites > Classic ASP.NET MVC with VSF (very rare)

Attack Surface Signals

Response headers indicating ASP.NET:

X-AspNet-Version: 4.0.30319          (classic — disclosure on its own)
X-Powered-By: ASP.NET
X-AspNetMvc-Version: 5.2
Server: Microsoft-IIS/10.0
Set-Cookie: ASP.NET_SessionId=...
Set-Cookie: .ASPXAUTH=...            (Forms auth cookie)
Set-Cookie: .ASPXFORMSAUTH=...
Set-Cookie: ASP.NET_SessionId=...; SameSite=None  (suggests cross-origin embedding)

Body signals (in form HTML):

<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="..." />
<input type="hidden" name="__VIEWSTATEGENERATOR" id="__VIEWSTATEGENERATOR" value="..." />
<input type="hidden" name="__VIEWSTATEENCRYPTED" id="__VIEWSTATEENCRYPTED" value="" />
                                        ↑ EMPTY = signed-only, not encrypted = exploitable if key leaks
<input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="..." />
<input type="hidden" name="__REQUESTDIGEST" id="__REQUESTDIGEST" value="0x...,...">
                                        ↑ SharePoint CSRF token; if anon-issued, see hunt-sharepoint

Read the full file on GitHub · 322 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

7d ago First seen · 322 lines · 98 tokens per session scan A 3fac1d822757

Subscribe to this mod's changes

hunt-aspnet is a skill published in the GitHub repository uphiago/recon-skills (1,254 stars, last pushed 9d ago), licensed MIT. It adds 98 tokens to every session and 5,670 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

Backend and APIs Security aspnet bug-bounty cloud-security cors-exploitation firebase-hacking hermes-agent hunt jwt-attacks redteam web

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