JetBrains Junie GitHub Action prompt injection vulnerability

A prompt injection protection bypass vulnerability was discovered in JetBrains Junie GitHub Action before version 1.6.4, which could be exploited using HTML-encoded characters.

Disclosed 6 November 2026 · Record updated 6 November 2026

Impact

Prompt injection protection could be bypassed via HTML-encoded characters in versions before 1.6.4

Our coverage

A robot assistant reads instructions written in invisible ink, following hidden commands woven into seemingly innocent text while its protective shield crumbles.

Vulnerabilities

JetBrains patches prompt injection bypass in Junie GitHub Action

A flaw tracked as CVE-2026-123851 let attackers slip past the coding agent's prompt injection defences using HTML-encoded characters, according to the NVD entry published on 6 November 2026.

6 Nov 2026

Sources

nvd.nist.govhttps://nvd.nist.gov/vuln/detail/CVE-2026-123851