CVE-2026-12048: pgAdmin 4: Stored XSS enables full browser session hijack

Stored cross-site scripting in pgAdmin 4's error-rendering and plan-node-rendering paths. Text returned by a PostgreSQL server (ErrorResponse messages, including object names quoted back inside relation-does-not-exist errors and inside EXPLAIN Recheck Cond / Exact Heap Blocks fields) was passed verbatim through html-react-parser at every user-facing sink — the notifier toasts, FormFooterMessage / FormInput help and error areas, FormNote, ModalProvider AlertContent and confirmDelete, ToolErrorView, the Explain visualiser's NodeText panel, the SQL editor confirm dialogs, ConfirmSaveContent, PreferencesHelper modal alerts, and SelectThemes helper text. A PostgreSQL server an attacker controls — or any server returning attacker-influenced text such as a table or column name a low-privilege database user can create — could inject arbitrary HTML (including <iframe>) into the pgAdmin DOM the moment the victim's pgAdmin connected to that server or viewed an Explain plan that referenced the crafted object. The injected iframe's srcdoc could fetch attacker-served JavaScript and, by writing to parent.location, redirect the victim's top-level pgAdmin browser tab to an attacker-controlled URL. Because the injection originates from inside pgAdmin's own interface, standard anti-clickjacking controls (X-Frame-Options, Content-Security-Policy: frame-ancestors) do not mitigate it. A phishing page rendered inside the legitimate pgAdmin window is indistinguishable from a genuine pgAdmin dialog. Fix combines three complementary layers. (1) DOMPurify sanitisation is wrapped around every html-react-parser call site reachable from notifier, alert, form-error, Explain, and SQL-editor flows. (2) A new plain-text rendering contract — SafeMessage / SafeHtmlMessage components plus Notifier.errorText / alertText / warningText / infoText / successText helpers — is introduced; around fifty callers across browser, tools, dashboard, debugger, misc, llm, preferences, schema diff, and the SQL editor that previously interpolated backend-derived strings are migrated to the plain-text variants. (3) Backend HTML-escape is applied at the post-connection-SQL handler (execute_post_connection_sql) via a new sanitize_external_text helper, so third-party JSON consumers (audit logs, API clients) never receive raw markup either; the Explain plan-info renderer is also patched to _.escape Recheck Cond and Exact Heap Blocks at construction (matching every sibling field), giving defence in depth even before DOMPurify runs. This issue affects pgAdmin 4: from 6.0 before 9.16.

An attacker with INSERT privilege on a shared PostgreSQL database used as a pgvector RAG store creates a table named with an embedded XSS payload: a name containing an iframe whose srcdoc attribute loads attacker-served JavaScript. When the DBA opens pgAdmin and executes any query that causes PostgreSQL to reference this table in a relation-does-not-exist error—routine during schema exploration or debugging—pgAdmin's notifier toast renders the table name verbatim via html-react-parser. The iframe loads attacker JavaScript inside pgAdmin's own origin: it reads the pgAdmin master password store and browser-stored credentials, exfiltrates connection strings for all registered servers (including production pgvector instances), and calls parent.location to replace the pgAdmin tab with an indistinguishable phishing login page. In an AI/ML context, this attack is trivially triggered during routine maintenance—running EXPLAIN ANALYZE on a vector similarity search query or browsing an embedding table in the schema browser—with no visual indication to the victim that anything malicious occurred.