# SA-2026-002: Links built from captured data had no scheme check

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Security advisory SA-2026-002 (medium, fixed): Links built from captured data had no scheme check.

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# SA-2026-002: Links built from captured data had no scheme check

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-79 |
| **Component** | `admin/build/build.py (links to sources, leads, tickets)` |
| **Found by** | security@php.newsroom |
| **Found** | 2026-10-22 |
| **Fixed in** | v0.5.5 |
| **Fixed by** | security@php.newsroom |

## What it is

Source URLs, leads and other links from data were HTML-escaped but not checked for their scheme, so a javascript: or data: URL would have become a clickable link.

## What an attacker could do

One click on a poisoned "original" link would run script on the site. No such URL was in the data.

**How:** A source row (from a captured page or a tip) carries url: "javascript:...". The build writes it into href.

## Root cause

Escaping was treated as sufficient for URLs; it stops attribute breakout, not dangerous schemes.

## What contributed
- URLs are the one field where escaping and validation are different jobs.

## What was not in place

A URL allow-list at the point where data becomes an href.

## The fix

U() lets through only http(s), mailto and relative URLs; everything else becomes "#".

## What prevents it now

The gate fails on javascript:, vbscript: and data:text/html in href, src and action; the CSP blocks javascript: URLs.


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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-2026-002/index.html