CVE-2026-48768: TypeBot: Unauthenticated arbitrary s3 object write in generate-upload-url via unsanitized fileName

Synopsis

An unauthenticated arbitrary file write vulnerability exists in TypeBot (versions 3.16.1 and earlier) via the unsanitized fileName parameter in the generate-upload-url API endpoint. The endpoint is reachable over the network with no authentication and accepts attacker-controlled input to construct S3 object keys, then issues presigned PUT URLs with no Content-Type binding. Successful exploitation allows an attacker to write arbitrary HTML, SVG, or JavaScript files to attacker-chosen S3 subpaths, enabling arbitrary content hosting and stored cross-site scripting (XSS) on the storage origin, including paths belonging to other tenants. No patched release has been published upstream; HarborGuard is tracking the advisory and will make a patched-image rebuild available as soon as a fix version is released.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable endpoint is exposed over the network; an attacker must be able to send HTTP requests to the TypeBot instance's public API surface.

• AuthenticationNot required

  The generate-upload-url endpoint performs no authentication check, so any anonymous client can reach it without credentials.

• Victim interactionNot required

  No victim action is needed; the attacker sends a crafted POST request directly to the API without requiring any user to click or open anything.

• Attack complexityDetail

  Exploitation is reliable and condition-free: the attacker supplies a forward-slash-injected fileName value and receives a valid presigned PUT URL in response, with no race condition or special environment state required.

Blast Radius

• Attacker writes arbitrary HTML, SVG, or JavaScript files to attacker-chosen subpaths on the shared S3 or MinIO storage origin, enabling malicious content to be served from a trusted storage domain.
• Attacker-placed scripts execute in the browser of any user whose browser loads a resource from the storage origin, enabling stored XSS that steals session tokens, cookies, or other in-browser credentials.
• Because object key paths are not tenant-scoped before the write, an attacker can overwrite or inject content into publicly served result paths belonging to other tenants on the same instance, affecting data belonging to organizations other than the attacker's own.
• Limited confidentiality exposure (CVSS C:L) means the presigned URL issuance flow may leak partial information about the storage key namespace and bucket structure to an unauthenticated caller.