Closed
Conversation
mhevery
requested review from
AndrewKushnir and
IgorMinar
and removed request for
IgorMinar
pullapprove
bot
added
area: core
|
|
mhevery
added
target: lts
pullapprove
bot
added
area: core
jelbourn
approved these changes
Dec 15, 2020
Member
jelbourn
left a comment
jelbourn
left a comment
There was a problem hiding this comment.
LGTM
Reviewed-for: fw-security
AndrewKushnir
approved these changes
Dec 15, 2020
Contributor
AndrewKushnir
left a comment
AndrewKushnir
left a comment
There was a problem hiding this comment.
LGTM, thanks for the fix @mhevery 👍
(just left a couple minor comments related to comments, nothing critical)
Contributor
Author
Escape the content of the strings so that it can be safely inserted into a comment node. The issue is that HTML does not specify any way to escape comment end text inside the comment. `<!-- The way you close a comment is with "-->". -->`. Above the `"-->"` is meant to be text not an end to the comment. This can be created programmatically through DOM APIs. ``` div.innerHTML = div.innerHTML ``` One would expect that the above code would be safe to do, but it turns out that because comment text is not escaped, the comment may contain text which will prematurely close the comment opening up the application for XSS attack. (In SSR we programmatically create comment nodes which may contain such text and expect them to be safe.) This function escapes the comment text by looking for the closing char sequence `-->` and replace it with `-_-_>` where the `_` is a zero width space `\u200B`. The result is that if a comment contains `-->` text it will render normally but it will not cause the HTML parser to close the comment.
gkalpak
reviewed
Dec 16, 2020
| */ | ||
|
|
||
| const END_COMMENT = /-->/g; | ||
| const END_COMMENT_ESCAPED = '-\u200B-\u200B>'; |
Member
There was a problem hiding this comment.
OOC, why use two \u200Bs? Wouldn't --\u200B> also work?
alxhub
removed
the
target: lts
alxhub
pushed a commit
that referenced
this pull request
Dec 16, 2020
Escape the content of the strings so that it can be safely inserted into a comment node. The issue is that HTML does not specify any way to escape comment end text inside the comment. `<!-- The way you close a comment is with "-->". -->`. Above the `"-->"` is meant to be text not an end to the comment. This can be created programmatically through DOM APIs. ``` div.innerHTML = div.innerHTML ``` One would expect that the above code would be safe to do, but it turns out that because comment text is not escaped, the comment may contain text which will prematurely close the comment opening up the application for XSS attack. (In SSR we programmatically create comment nodes which may contain such text and expect them to be safe.) This function escapes the comment text by looking for the closing char sequence `-->` and replace it with `-_-_>` where the `_` is a zero width space `\u200B`. The result is that if a comment contains `-->` text it will render normally but it will not cause the HTML parser to close the comment. PR Close #40136
This was referenced Dec 16, 2020
|
This issue has been automatically locked due to inactivity. Read more about our automatic conversation locking policy. This action has been performed automatically by a bot. |
This file contains hidden or 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
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
5 participants
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.
Escape the content of the strings so that it can be safely inserted into a comment node.
The issue is that HTML does not specify any way to escape comment end text inside the comment.
<!-- The way you close a comment is with "-->". -->. Above the"-->"is meant to be text not an end to the comment. This can be created programmatically through DOM APIs.One would expect that the above code would be safe to do, but it turns out that because comment text is not escaped, the comment may contain text which will prematurely close the comment opening up the application for XSS attack. (In SSR we programmatically create comment nodes which may contain such text and expect them to be safe.)
This function escapes the comment text by looking for the closing char sequence
-->and replace it with-_-_>where the_is a zero width space\u200B. The result is that if a comment contains-->text it will render normally but it will not cause the HTML parser to close the comment.PR Checklist
Please check if your PR fulfills the following requirements:
PR Type
What kind of change does this PR introduce?
What is the current behavior?
Issue Number: N/A
What is the new behavior?
Does this PR introduce a breaking change?
Other information