HedgeDoc is an open source, real-time, collaborative, markdown notes application. Prior to version 1.11.0, due to unsafe handling of the local-part of registered email addresses, HedgeDoc was vulnerable to stored HTML Injection through its publish and slide views. An attacker could register a specially crafted email address and inject arbitrary HTML into pages viewed by other users. HedgeDoc accepted RFC 5321 quoted-string local-parts in email addresses during registration. The local-part was then reused as the user's display name without escaping and rendered into HTML in multiple places, including publish and slide views as well as the collaborative editor. An attacker could break out of an HTML attribute and inject arbitrary markup into the page. While the deployed Content-Security-Policy prevented straightforward inline JavaScript execution, the injected HTML was still sufficient to alter page content and embed attacker-controlled resources such as cross-origin iframes. This issue was fixed in version 1.11.0.

HedgeDoc is an open source, real-time, collaborative, markdown notes application. Prior to version 1.11.0, HedgeDoc was vulnerable to a YAML alias bomb due to unsafe processing of the note frontmatter. HedgeDoc parsed frontmatter with js-yaml.load (js-yaml v3) via @hedgedoc/meta-marked, which resolved YAML anchor aliases. A compact malicious payload could therefore expand into a huge object structure, consuming excessive CPU. This expansion ran on every request to the publish view (/s/<shortid>) and, when placed under the opengraph key, the editor view (/<noteId>). A ten-level alias bomb could block the single Node.js event loop for roughly 235 seconds per request, causing concurrent requests to hang or drop and rendering the instance unavailable (DoS). Because the note was stored in the database, the impact survived process restarts until the note was removed. toobusy-js did not reliably mitigate the worst cases, as the event loop was saturated before the middleware could respond. This issue was fixed in version 1.11.0.

HedgeDoc is an open source, real-time, collaborative, markdown notes application. Versions prior to 1.11.0 allowed attackers to circumvent the rate-limiting of the /login and /register routes by spoofing IP addresses. HedgeDoc instances checked for CloudFlare's cf-connecting-ip header and used that instead of the users real IP address, if the header was present even when the request did not originate from Cloudflare. This made it possible for an attacker to spam login requests or create multiple arbitrary accounts by sending another cf-connecting-ip header every few requests. The issue has been fixed in version 1.11.0.

HedgeDoc is an open source, real-time collaborative markdown notes application. Prior to 1.11.0, the GitHub Gist export flow created an OAuth2  state  value but only checked that it was present rather than validating it against the value expected for the user's session. Because the state was not properly validated, an attacker could forge a callback URL containing their own valid GitHub OAuth code. When processing the callback, HedgeDoc used the victim's logged-in session to select which note to export, but the attacker's authorization code to determine which GitHub account received it. As a result, a logged-in victim who clicked a crafted link could export their own private, protected, or limited note directly into a Gist controlled by the attacker. This issue has been fixed in version 1.11.0.