Vulnerability · Published May 26, 2026 · Assigned by VulDB

CVE-2026-9520blitz-js blitz Sign-in LoginForm.tsx cross site scripting

Medium 4.3

In plain English

A medium-severity cross-site scripting in blitz from blitz-js. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.3%top 72.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

A weakness has been identified in blitz-js blitz up to 3.0.2 on GitHub. This impacts an unknown function of the file packages/generator/templates/app/src/app/auth/components/LoginForm.tsx of the component Sign-in. This manipulation of the argument Next causes cross site scripting. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	blitz	no fix listed	GHSA-h2p9-cr4h-px24

Affected products (as reported)

Vendor	Product	Versions
blitz-js	blitz	3.0.03.0.13.0.2

Weakness: CWE-79, CWE-94 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N/E:P/RL:X/RC:R

References

VDB-365540 | blitz-js blitz Sign-in LoginForm.tsx cross site scripting vdb-entry, technical-description
VDB-365540 | CTI Indicators (IOB, IOC, TTP, IOA) signature, permissions-required
Submit #814378 | BlitzJS Blitz 3.0.2 DOM-Based XSS, Open Redirect third-party-advisory
https://gist.github.com/TrebledJ/164c7ca6c8208b63e6937bc11984720b exploit