# SA-2026-021: The vault app: prototype pollution and javascript: links from vault data

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Security advisory SA-2026-021 (medium, fixed): The vault app: prototype pollution and javascript: links from vault data.

[Advisories](../index.html) / SA-2026-021

# SA-2026-021: The vault app: prototype pollution and javascript: links from vault data

Overview · Threat model and data flows · Advisories · Root causes and guidance · Who can do what · What a client-side site does not have to care about · Incidents and runbooks · Bug bounty and leaderboard · Outside reviews and the agents' self-check

|  |  |
|---|---|
| **Severity** | medium |
| **Status** | fixed |
| **Weakness** | CWE-1321 |
| **Component** | `vault-app/src/index.html.tpl` |
| **Found by** | security@php.newsroom (pass 3 review) |
| **Found** | 2026-10-24 |
| **Fixed in** | v0.14.26 |
| **Fixed by** | security@php.newsroom |

## What it is

Filter presets built from vault values were parsed and merged with Object.assign for every key, __proto__ included, polluting objects later written into markup. Source URLs went into href with no scheme check.

## What an attacker could do

Script inside the vault app, with read access to the vault's files (it has no CSP).

**How:** A vault writer adds a source kind or agent name that breaks out of the preset JSON.

## Root cause

Merging untrusted objects without a key allow-list.

## What contributed
- The vault app runs on another origin, outside this site's CSP and gate.

## What was not in place

Allow-listed merges; URL scheme checks in every renderer.

## The fix

Presets keep only the four views' known filters with string or null values; source links are http(s) only.

## What prevents it now

Proposed: a CSP for the vault app.


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site v0.18.0 · data as of 2026-10-24T16:05Z · vault commit 8c16a64a7cf6 · https://php.oct.2026.newsroom.sgit.ai/admin/appsec/advisories/SA-2026-021/index.html