Affected: jhipster generator-jhipster, jhipster react-jhipster

JHipster is a development platform to quickly generate, develop, and deploy modern web applications and microservice architectures. Prior to generator-jhipster 9.4.0 and react-jhipster 1.1.0, generated applications can persist attacker-controlled Blob data and companion ContentType values, return them through generated REST endpoints, and pass them to the generated openFile helper in generators/client/generators/common/templates/src/main/webapp/app/shared/jhipster/data-utils.ts.ejs. The helper uses the returned ContentType as the browser Blob MIME type and opens an object URL, so a normal authenticated user with write access to a Blob-bearing entity can store active HTML or SVG content that may execute under the application origin when a privileged user opens it. Exploitability depends on the generated application's content security policy and target-browser Blob behavior. This issue is fixed in generator-jhipster 9.4.0 and react-jhipster 1.1.0.

Affected: npm: generator-jhipster, npm: react-jhipster

## Summary Applications generated by generator-jhipster v9.2.0 can persist user-controlled Blob ContentType values and later use those values as the MIME type for client-side Blob objects. The shared generated `openFile` helper creates an object URL from the Blob and opens it in a new window.

For Blob-bearing entities writable by normal authenticated users, this creates a stored XSS chain: attacker-controlled Blob content and MIME type are stored through the generated REST API, returned to privileged users, and opened as a same-origin Blob document from the generated Angular/React/Vue UI. Exploitability should be confirmed against the generated app’s CSP and target browsers.

## Details The root cause is a trust-boundary failure across generated server and client code. The generated entity REST resource accepts request bodies for entity creation and update. Unless an entity-specific authority is configured, the template omits method-level `@PreAuthorize`, leaving the endpoint available to any authenticated user under the global `/api/**` security rule.

The generated DTO/domain/mapper flow stores the companion `<field>ContentType` property as a plain `String` and persists it with the entity Blob data. The relevant templates include `generators/spring-boot/templates/src/main/java/_package_/_entityPackage_/service/dto/_dtoClass_.java.ejs:96-122` and `generators/java/generators/domain/templates/src/main/java/_package_/_entityPackage_/domain/_persistClass_.java.jhi.ejs:124-140`…