imported>Mrqwerty567: /* Exploits */ fixed dead link for ref 8

2025-10-13T00:50:45Z

Exploits: fixed dead link for ref 8

New page

{{short description|Web page archive (file) format}}
{{more citations needed|date=April 2014}}
{{Infobox file format
| name = MHTML
| icon =
| screenshot =
| extension = .mht, .mhtml
| mime = {{ubl|class=nowrap|multipart/related|application/x-mimearchive|message/rfc822}}
| type code =
| uniform type =
| owner =
| genre = [[Markup language]]
| container for =
| contained by =
| extended from = [[HTML]]
| extended to =
| standard = {{nowrap|RFC 2557 {{smaller|(proposed 1999)}}}}
}}

'''MHTML''', an [[initialism]] of "[[MIME]] encapsulation of aggregate [[HTML]] documents", is a [[List of web archiving file formats|web archiving file format]] used to combine, in a single [[computer file]], the HTML code and its companion resources (such as images) that are represented by external [[hyperlink]]s in the web page's HTML code. The content of an MHTML file is encoded using the same techniques that were first developed for [[HTML email]] messages, using the MIME content type <code>multipart/related</code>.<ref>{{cite web |first=Amanda |last=Holden |title=Difference of HTML & MHTML |url=https://www.techwalla.com/articles/difference-of-html-mhtml |access-date=17 November 2017 |archive-url=https://web.archive.org/web/20171117122700/https://www.techwalla.com/articles/difference-of-html-mhtml |archive-date=17 November 2017 |url-status=dead}}</ref> MHTML files use an <code>.mhtml</code> or <code>.mht</code> [[filename extension]].

The first part of the file is an [[e-mail header]]. The second part is normally HTML code. Subsequent parts are additional resources identified by their original [[URL|uniform resource locator]]s (URLs) and encoded in [[base64]] [[binary-to-text encoding]]. MHTML was proposed as an open standard, then circulated in a revised edition in 1999 as RFC 2557.

The <code>.mhtml</code> and <code>[[Email#Filename extensions|.eml]]</code> filename extensions are interchangeable: either filename extension can be changed from one to the other. An .eml message can be sent by e-mail, and it can be displayed by an [[email client]]. An email message can be saved using a <code>.mhtml</code> or <code>.mht</code> filename extension and then opened for display in a [[web browser]] or for editing other programs, including [[word processor]]s and [[text editor]]s.

== Layout ==
The header of an MHTML file contains [[Metadata#File metadata|metadata]] such as a [[time stamp|date and time stamp]], page title, the source URL, and a unique randomized boundary string for separating resources contained within the file. The boundary string is defined at the beginning and used throughout the file.

<syntaxhighlight lang="email">
From: <Saved by Blink>
Snapshot-Content-Location: https://en.wikipedia.org/wiki/Smartphone
Subject: Smartphone - Wikipedia
Date: Sat, 24 Sep 2022 00:34:32 -0000
MIME-Version: 1.0
Content-Type: multipart/related;
type="text/html";
boundary="----MultipartBoundary--GsIBda0vjy2AKIAIliwl7JMwezXDRjDAsLje9khd5l----"
</syntaxhighlight>

Then, the page resources are contained sequentially, starting with the page's rendered HTML source code. Each resource has its own metadata header which specifies its [[MIME type]] and the original location.

<syntaxhighlight lang="email">
------MultipartBoundary--GsIBda0vjy2AKIAIliwl7JMwezXDRjDAsLje9khd5l----
Content-Type: text/html
Content-ID: <frame-D968CEC8BB7E60A1859261A8CA5DFB4D@mhtml.blink>
Content-Transfer-Encoding: binary
Content-Location: https://en.wikipedia.org/wiki/Smartphone

<!DOCTYPE html>
</syntaxhighlight>

The MHTML file ends with a boundary string that is not followed by any data.<ref>{{cite web |title=2. The MHTML File Format - Hunchly Knowledge Base |url=https://support.hunch.ly/article/51-1-the-mhtml-file-format |website=support.hunch.ly |access-date=24 September 2022 |date=October 17, 2018}}</ref>

== MIME type ==
MIME type for MHTML is not well agreed upon. Used MIME types include:
* <code>multipart/related</code>
* <code>application/x-mimearchive</code>
* <code>message/rfc822</code>

== Supporting apps ==
=== Web browsers ===
Some browsers support the MHTML format, either directly or through third-party extensions, but the process for saving a web page along with its resources as an MHTML file is not standardized. Due to this, a web page saved as an MHTML file using one browser may render differently on another.

* '''[[Internet Explorer 5]]''' was the first browser to support reading and saving web pages and external resources to a single MHTML file.
* '''[[Microsoft Edge]]''', after switching to the Chromium source code, supports saving web pages as MHTML.
* '''[[Opera (web browser)|Opera]]:''' Support for saving web pages as MHTML files was made available in the Opera 9.0 web browser.<ref>{{cite web|url=http://my.opera.com/desktopteam/blog/show.dml/172375 |title=…and one more weekly! |last=Santambrogio |first=Claudio |date=10 March 2006 |publisher=[[Opera Software]] |access-date=2009-05-15 |archive-url=https://web.archive.org/web/20100115001636/http://my.opera.com/desktopteam/blog/show.dml/172375 |archive-date=15 January 2010 |url-status=dead }}</ref> From Opera 9.50 through the rest of the Presto-based Opera product line (version 12.16 as of 19 July 2013), the default format for saving pages is MHTML. The initial release of the new Webkit/Blink-based Opera (version 15) did not support MHTML, but subsequent releases (16 and later) do. MHTML can be enabled by typing "<code>opera://flags#save-page-as-mhtml</code>" at the address bar.
* '''[[Google Chrome]] 86''' and later can create MHTML files.
* '''[[Yandex Browser]] 22.7.4.960''' (July 2022) and later can create MHTML (multipart/related) files.
* '''[[Vivaldi (web browser)|Vivaldi]] 2.3 and later''' can create MHTML files.<ref>{{Cite web|url=https://vivaldi.com/fr/blog/auto-stacking-tabs/|title=Vivaldi Update {{!}} Auto-Stacking Tabs|last1=février 6|first1=Publié sur|last2=Tetzchner|first2=2019-Par Jon von|date=2019-02-06|website=Vivaldi|language=fr|access-date=2019-05-16}}</ref> It supports both reading and writing MHTML files by toggling the "<code>vivaldi://flags/#save-page-as-mhtml</code>" option.
* '''[[Firefox]]''' does not support MHTML.<ref>{{cite web|title=Bug 40873 - Save as rfc 2557 MHTML; complete webpage in one file|url=https://bugzilla.mozilla.org/show_bug.cgi?id=40873}}</ref> Until [[Firefox version history#Firefox 52 through 59|version 57 ("Firefox Quantum")]], two [[browser extension]], Mozilla Archive Format or UnMHT, could read and write MHTML files. These extensions are incompatible with version 57 and later.
* '''[[Safari (web browser)|Safari]] 3.1.1 and later''' terminated native support for the MHTML format. Instead, the browser supports the [[Web Archive (file format)|Web Archive]] format. The [[macOS]] version includes a print-to-[[PDF]] feature. As with most other modern web browsers, support for MHTML files can be added to Safari via various third-party extensions.
* '''[[Konqueror]] 3.5.7 and later''' terminated support for MHTML files. An extension project, <code>mhtconv</code>, can be used to allow saving and viewing of MHTML files.
* '''[[NetFront]] 3.4''' (on devices such as the Sony Ericsson [[K850]]) can view and save MHTML files.
* '''[[Pale Moon (web browser)|Pale Moon]]''' requires an extension to be installed to read and write MHT files. One extension is freely available, MozArchiver, a fork of Mozilla Archive Format extension.
* '''[[GNOME Web]]''' added support for read and save web pages in MHTML since version 3.14.1 released in September 2014.<ref>{{Cite web|url=https://gitlab.gnome.org/GNOME/epiphany/blob/master/NEWS#L1061|title = NEWS · master · GNOME / Epiphany| date=28 July 2023 }}</ref>

=== Other apps ===
* [[Problem Steps Recorder]] for Windows can save its output to MHT format.
* The "Save to Google Drive" extension for [[Google Chrome]] can save as MHTML as one of its outputs.
* [[Microsoft OneNote]] 2010 and later can email individual pages as .mht files.
* [[Evernote]] for Windows can export notes as MHT format, as an alternative to HTML or its own native .enex format.

== Exploits ==
In May 2015, a researcher noted that attackers could build malicious documents by creating an MHT file, appending an MSO object at the end (MSO is a file format used by the [[Microsoft Outlook]] e-mail application), and renaming the resulting file with a .doc extension.<ref>{{Cite web|url=https://www.securityweek.com/attackers-hide-malicious-macros-mhtml-documents|title=Attackers Hide Malicious Macros in MHTML Documents|last=Kovacs|first=Eduard|date=May 11, 2015|website=SecurityWeek.Com|access-date=April 19, 2019}}</ref> The delivery method would be by spam emails.<ref>{{Cite web |last=Mosuela |first=Lordian |date=July 10, 2015 |title=New Tricks of Macro Malware |url=https://www.cyren.com/blog/articles/new-tricks-of-macro-malware |url-status=dead |archive-url=https://web.archive.org/web/20240908105634/https://data443.com/blog/cyren/new-tricks-of-macro-malware/ |archive-date=September 8, 2024 |access-date=April 19, 2019 |website=Cyren |language=en}}</ref>

In April 2019, a security researcher published details about an [[XML external entity attack|XML external entity (XXE) vulnerability]] that could be exploited when a user opens an MHT file. Since the Windows operating system is set to automatically open all MHT files, by default, in Internet Explorer, the exploit could be triggered when a user double-clicked on a file that they received via email, instant messaging, or another vector, including a different browser.<ref>{{Cite web|url=https://www.zdnet.com/article/internet-explorer-zero-day-lets-hackers-steal-files-from-windows-pcs/|title=Internet Explorer zero-day lets hackers steal files from Windows PCs|last=Cimpanu|first=Catalin|date=April 12, 2019|website=[[ZDNet]]|language=en|access-date=April 19, 2019}}</ref>

== Alternatives ==
=== Data URI scheme ===
The [[data URI scheme]] offers an alternative for including separate elements such as images, [[Style sheet (web development)|style-sheets]] and scripts in-line when serving an HTML request or saving an HTML resource for offline use. Like the embedded content within MHTML, data URIs use [[Base64]] encoding of the external resources (which may be binary or text) to embed them in-line within the HTML markup. HTML pages saved with external elements embedded using the [[data URI scheme]] are standard web pages, and can be opened by any modern browser, including browsers not supporting MHTML such as Mozilla Firefox.<ref>{{cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URLs#browser_compatibility|title=Data URLs - HTTP|website=MDN|language=en|access-date=April 2, 2023}}</ref> Unlike MHTML, saving web pages with their external resources embedded using data URIs requires a third-party extension to be installed in the browser.<ref>{{cite web|url=https://www.ghacks.net/2018/09/03/save-any-webpage-as-a-single-file-in-chrome-or-firefox/|title=Save any webpage as a single file in Chrome or Firefox - gHacks Tech News|last=Brinkmann|first=Martin|date=September 3, 2018|website=ghacks.net|language=en|access-date=April 2, 2023}}</ref>

=== Mozilla Archive Format ===
The [[Mozilla Archive Format]] (MAFF) is a legacy Web archive file format that was supported by Firefox from 2004 to 2018 through an add-on.<ref>{{cite web|url=https://www.amadzone.org/mozilla-archive-format/|title=Mozilla Archive Format Add-on - File Format Overview|website=amadzone|language=en|access-date=April 2, 2023}}</ref> Unlike both MHTML and data URIs, MAFF uses a [[ZIP (file format)|ZIP]] container to preserve both the HTML file and its external elements. In October 2017 the add-on developer announced the format would no longer be supported in future versions of Firefox.<ref>{{cite web |url= https://addons.mozilla.org/en-US/firefox/addon/mozilla-archive-format/|title=Firefox Addon: MAF - Mozilla Archive Format|accessdate=2 April 2023 |url-status=dead |archive-url=https://web.archive.org/web/20171102005204/https://addons.mozilla.org/en-US/firefox/addon/mozilla-archive-format/ |archive-date=2 November 2017}}</ref>

== See also ==
* [[data URI scheme]]
* [[Mozilla Archive Format]]
* [[Web Archive (file format)|Web Archive format]]
* [[WARC (file format)|WARC format]]

== References ==
{{Reflist}}

==External links==
* [http://www.dsv.su.se/~jpalme/ietf/mhtml.html MHTML standard explained]
* [https://datatracker.ietf.org/doc/rfc2557/ RFC 2557] (1999)—MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)
* [https://datatracker.ietf.org/doc/rfc2110/ RFC 2110] (1997, Obsolete)—MIME E-mail Encapsulation of Aggregate Documents, such as HTML (MHTML)

{{web browsers}}
{{Internet Explorer}}
{{Microsoft Office}}

[[Category:Archive formats]]
[[Category:Internet Explorer]]
[[Category:HTML]]
[[Category:MIME]]
[[Category:Web archives]]

MHTML - Revision history

imported>Mrqwerty567: /* Exploits */ fixed dead link for ref 8