{"items":[{"id":"NVI-00018349","kind":"vulnerability","title":"Sveltia CMS: Stored XSS in Markdown/RichText preview via unsandboxed same-origin iframe","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-h5jc-78hr-3pc9"],"plain_summary":"GitHub lists this reviewed advisory for @sveltia/cms. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-14a476e5589de06f96986e68c1f074fd"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-14a476e5589de06f96986e68c1f074fd","url":"https://github.com/advisories/GHSA-h5jc-78hr-3pc9","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-h5jc-78hr-3pc9","publisher":"GitHub Advisory Database","observed_at":"2026-11-06T07:18:46.322Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-14a476e5589de06f96986e68c1f074fd"],"technology":"@sveltia/cms","known_exclusions":[],"conditions_summary":"### Impact\n\nA stored cross-site scripting (XSS) vulnerability affected the Markdown/RichText field preview renderer in Sveltia CMS.\n\nThe DOMPurify sanitization configuration used for Markdown previews explicitly permitted `iframe` elements without enforcing a `sandbox` attribute or restricting iframe sources. Sanitized Markdown output was then inserted into the CMS preview DOM as raw HTML. Because no sandboxing or source validation was applied, a Markdown field containing an `iframe` whose src pointed to a same-origin uploaded or publicly accessible HTML asset would render an unsandboxed iframe. JavaScript in the framed document could then access the parent CMS window via the browser’s same-origin policy, allowing it to read and write the parent window’s state, DOM, and browser storage, and to trigger actions in the CMS context.\n\nThe practical impact is limited in currently supported Sveltia CMS usage because the CMS is intended for a single developer or a small trusted team, and open authoring / untrusted multi-user authoring is not currently implemented. Exploitation requires the ability to place malicious content into the reposito","public_affected_ranges":["< 0.167.3"]}],"null_published_at":"2026-11-07T07:07:39.821Z","source_updated_at":"2026-06-19T21:42:20.000Z","source_disclosed_at":"2026-06-19T21:42:20.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-06T07:18:46.322Z"}],"next_cursor":null,"snapshot_revision":"42594"}