Fix secondary order XSS: Harden file type inputs #4635
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
I can't detect whether a file is CSS. However, I can add some CSS trash as first line of a so called CSS file. If JS run, it will just crash first line... will do this. |
|
Ok I managed to make uploaded JS unexecutable with |
Comment on lines
+708
to
+710
| if (model.CssFile.Length > 1_000_000) | ||
| { | ||
| TempData[WellKnownTempData.ErrorMessage] = "The uploaded file should be less than 1MB"; |
There was a problem hiding this comment.
We can lower this limit here as 100KB should already be more than enough. (Bootstrap as a whole is > 300KB)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
I was thinking we could avoid validating file upload.
But nope... @nayefhmoodh has shown me a secondary order XSS which can even avoid the strictest CSP by crafting a rogue PDF file...
Credit to @nayefhmoodh
https://huntr.dev/bounties/9464e3c6-961d-4e23-8b3d-07cbb31de541/