What are the dangers of "application/octet-stream" and what precautions can be taken?

### MDN URL

https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types/Common_types

### What specific section or headline is this issue about?

The two important MIME types are the default types: (Common media types)

### What information was incorrect, unhelpful, or incomplete?

the page states:

> application/octet-stream is the default value for all other cases. An unknown file type should use this type. Browsers are particularly careful when manipulating these files to protect users from software vulnerabilities and possible dangerous behavior.

### What did you expect to see?

Given the website is hosted on developper mozilla.org, the normative reference for what did it mean for the first date of writing the following fragement of the sentence _"Browsers are particularly careful when manipulating these files"_, that is, how Mozilla Firefox by default manipulates files of this default, common media type "application/octet-stream" both in technical as well as in simple language. Same for what _"parcicularly"_ and _"carfeul"_ means in this context — all are missing.

Additionally, the information in simple language is missing which software vulnerabilities were documented here (and technical hypertext reference for both classification as well as most common concrete examples are not adequate for a hypermedia as text/html the documentation announces itself under, further- or firstmore.)

Finally, what is the possible dangerous behaiour Mozilla Firefox did impose at the time of writing this sentence?

Is by this major default mimetype, Mozilla Firefox generally dangerous to use and can this be exploited by _not_ providing the appropriate mime-type?

How does Mozilla Firefox protect against re-starting itself when handling a mime-type as an application after downloading a file and starting Mozilla Firefox itself again to handle the downloaded file? (DDOS/local resource exhaustion/preventing user control)

### Do you have any supporting links, references, or citations?

For technical normative references, please use internet standards (IETF), for everything else hypertext references.

### Do you have anything more you want to share?

_No response_

### MDN metadata

Page report details

* Folder: `en-us/web/http/guides/mime_types/common_types`
* MDN URL: https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types/Common_types
* GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/http/guides/mime_types/common_types/index.md
* Last commit: https://github.com/mdn/content/commit/7e52ccf8751ee9f4b3dd4a466979418af48c1fbe
* Document last modified: 2025-06-09T02:13:48.000Z