GHSA-prjf-86w9-mfqv
MEDIUMAngular i18n vulnerable to Cross-Site Scripting
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
@angular/core📦@angular/core📦@angular/core📦@angular/core📦@angular/coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
A Cross-site Scripting (XSS) vulnerability has been identified in the Angular internationalization (i18n) pipeline. In ICU messages (International Components for Unicode), HTML from translated content was not properly sanitized and could execute arbitrary JavaScript.
Angular i18n typically involves three steps, extracting all messages from an application in the source language, sending the messages to be translated, and then merging their translations back into the final source code. Translations are frequently handled by contracts with specific partner companies, and involve sending the source messages to a separate contractor before receiving final translations for display to the end user.
If the returned translations have malicious content, it could be rendered into the application and execute arbitrary JavaScript.
Impact
When successfully exploited, this vulnerability allows for execution of attacker controlled JavaScript in the application origin. Depending on the nature of the application being exploited this could lead to:
- Credential Exfiltration: Stealing sensitive user data stored in page memory, LocalStorage, IndexedDB, or cookies available to JS and sending them to an attacker controlled server.
- Page Vandalism: Mutating the page to read or act differently than intended by the developer.
Attach Preconditions
- The attacker must compromise the translation file (xliff, xtb, etc.).
- Unlike most XSS vulnerabilities, this one is not exploitable by arbitrary users. An attacker must first compromise an application's translation file before they can escalate privileges into the Angular application client.
- The victim application must use Angular i18n.
- The victim application must use one or more ICU messages.
- The victim application must render an ICU message.
- The victim application must not defend against XSS via a safe Content-Security Policy (CSP) or Trusted Types.
Patches
- 21.2.0
- 21.1.6
- 20.3.17
- 19.2.19
Workarounds
Until the patch is applied, developers should consider:
- Reviewing and verifying translated content received from untrusted third parties before incorporating it in an Angular application.
- Enabling strict CSP controls to block unauthorized JavaScript from executing on the page.
- Enabling Trusted Types to enforce proper HTML sanitization.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @angular/core | ≥ 21.2.0-next.0&&< 21.2.0 | 21.2.0 |
| 📦npm | @angular/core | ≥ 21.0.0-next.0&&< 21.1.6 | 21.1.6 |
| 📦npm | @angular/core | ≥ 20.0.0-next.0&&< 20.3.17 | 20.3.17 |
| 📦npm | @angular/core | ≥ 19.0.0-next.0&&< 19.2.19 | 19.2.19 |
| 📦npm | @angular/core | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @angular/core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @angular/core to 21.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-prjf-86w9-mfqv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-prjf-86w9-mfqv is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-prjf-86w9-mfqv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-prjf-86w9-mfqv in your dependencies?
O3 detects GHSA-prjf-86w9-mfqv across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.