Type name: image Subtype name: wmf Required parameters: None. Optional parameters: DEFAULT_CHARSET: The character set intended when the CharacterSet enumeration (see the WMF specification) specifies DEFAULT_CHARSET. The value of this parameter is a charset from the IANA "Character Sets" registry . When this parameter is not specified, DEFAULT_CHARSET has the following meaning in the WMF specification: "a character set based on the current system locale; for example, when the system locale is United States English, the default character set is ANSI_CHARSET" (which is Windows-1252, more or less). That is, when not specified, the default character set is system dependent. This optional parameter is new to this registration and may not enjoy widespread support for some time. Therefore, EMF instead of WMF (or if necessary under the circumstances, embedded EMF within WMF) is a more sensible choice when text is present. Encoding considerations: Binary. Security considerations: The Windows Metafile format's security history is punctuated in 2005-2006 with the disclosure of the Metafile Image Code Execution ("MICE") vulnerability. MICE won the 2007 Pwnie Award for "Mass 0wnage" and "Breaking the Internet". The official Microsoft security bulletin describes that the flaw occurs because Windows Metafiles can set the SETABORTPROC value of the MetafileEscapes enumeration (accessible via the META_ESCAPE record), allowing for arbitrary code execution, i.e., "active content". Windows Metafiles can contain Enhanced Metafiles using the META_ESCAPE_ENHANCED_METAFILE record; thus, the security considerations of EMF apply to WMF. Windows Metafiles are historically very buggy. As the original intent was to replicate Windows GDI calls, flaws in GDI, or in a display or printer driver implementing the backend to GDI, could be exploitable. WMF implementations not backed by Windows GDI have different risks: namely, while a malicious WMF author may not consider the non-Windows GDI implementation as a primary target, WMF has many "corner case" records for which an implementation's processing may not have received the same level of scrutiny as the Windows implementation. "Fuzzing" the implementation is appropriate. As a "basic" image format, the image/wmf media type does not employ executable content and provides no facilities for privacy or integrity. Interoperability considerations: Windows Metafile is the original 16-bit metafile format; it was released in 1990 at what some computer historians might consider the "zenith" of the desktop publishing revolution. Accordingly, there is a large body of free and commercially available clip art that is still in use, either independently or embedded in productivity documents (word processing documents, desktop publishing documents, slideshows, presentations, spreadsheets, and workbooks). For example, references to WMF content appear (non- normatively) in Office Open XML. To say that support for this format is necessary for interoperability would not be an understatement. Accommodations for comments or arbitrary data storage in Windows Metafiles are virtually non-existent. However, Windows Metafiles can contain Enhanced Metafiles using the META_ESCAPE_ENHANCED_METAFILE record, so an implementation that handles Windows Metafiles is also expected to handle enhanced metafile content. Windows Metafiles can store and output text strings (see META_TEXTOUT and META_EXTTEXTOUT records), but the encodings of the strings may be ambiguous. Unicode encodings are not possible without the DEFAULT_CHARSET parameter defined in this registration. The previously unregistered type image/x-wmf is also in wide use. Accordingly, it is registered as a deprecated alias. Published specification: WMF: Microsoft Corporation, "[MS-WMF]: Windows Metafile Format", v20160714 (Rev 13.1), July 2016, . Applications that use this media type: Office productivity applications; clip art applications; desktop publishing applications; some web browsers (e.g., Internet Explorer). Fragment identifier considerations: None. Additional information: Deprecated alias names for this type: image/x-wmf Magic number(s): D7 CD C6 9A (little-endian DWORD 0x9AC6CDD7) File extension(s): .wmf Macintosh file type code(s): None. A uniform type identifier (UTI) of "com.microsoft.wmf" is suggested. Person & email address to contact for further information: Sean Leonard Restrictions on usage: None. Author/Change controller: Sean Leonard Intended usage: COMMON Provisional registration? No