(registered 2026-10-22, last updated 2026-10-22)

Media type name: application

Media subtype name: vnd.penguin-pn.theuip

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: binary

Security considerations: This media type does not contain active or executable content. The payload is a zlib-compressed JSON document that is transformed into CSS by the client application. However, CSS generated from this data can potentially be used for UI redressing or style-based injection attacks. Therefore, client applications MUST sanitize the generated CSS before applying it.

Privacy services are not required, as the format does not contain personal or sensitive data. Integrity services are recommended to prevent tampering with theme data. Implementations SHOULD verify the integrity of the decompressed payload using available checksums or digital signatures. Additionally, to prevent denial-of-service attacks via decompression bombs (zip bombs), implementations MUST enforce a strict maximum size limit on the decompressed zlib payload.

For untrusted sources, theme files SHOULD be processed in a sandboxed environment to mitigate potential risks. The decompressed JSON payload MUST be validated against a schema before parsing to prevent unexpected data structures or parser abuse.

Interoperability considerations: N/A

Published specification: https://github.com/Penguin-Pn/web_message/blob/main/theuip.md

Applications which use this media: Penguin Web Messaging application and its associated theme editor and parser tools.

Fragment identifier considerations: N/A

Restrictions on usage: N/A

Additional information:

1. Deprecated alias names for this type: N/A
2. Magic number(s): 0x89 54 48 45 55 49 50 0A
3. File extension(s): .theuip
4. Macintosh file type code: N/A
5. Object Identifiers: N/A

Person to contact for further information:

1. Name: Penguin Web Messaging Maintainer
2. Email: 6mmmmm31&gmail.com

Intended usage: LIMITED USE

The internal JSON schema is proprietary and not publicly documented. This format is exclusively used by Penguin Web Messaging.

Author/Change controller: Penguin Web Messaging