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HTML API: Reduce skip_script_data length checks #9230

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HTML API: Reduce skip_script_data length checks #9230

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6ad9951
Move script data length checks to top of loop
sirreal Jul 10, 2025
b3b3177
Remove parser_state change in skip_script_data
sirreal Jul 10, 2025
ca16e0e
Remove more length checks
sirreal Jul 10, 2025
0456be7
Improve documentation
sirreal Jul 10, 2025
ea6f7d3
Improve comment explaining early return logic
sirreal Jul 31, 2025
4be62b9
Improve loop comment
sirreal Aug 6, 2025
df2affa
Add script tag processing tests
sirreal Aug 6, 2025
d0cbb00
Remove problematic tests
sirreal Aug 6, 2025
aaa6763
Reword explanatory comment.
dmsnell Aug 6, 2025
f7d4b8e
Move script parsing adjacent to other script parsing test
sirreal Aug 7, 2025
c3c76d6
Merge branch 'trunk' into html-api/improve-skip-script-data-len-checks
sirreal Aug 7, 2025
34c3b28
Continue to tweak comment and improve examples
sirreal Aug 7, 2025
325bcb8
Merge branch 'trunk' into html-api/improve-skip-script-data-len-checks
sirreal Aug 7, 2025
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Move script data length checks to top of loop
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@sirreal
sirreal committed Aug 6, 2025
commit 6ad9951fd97873227a3ed23fa28910af72f73fc4
16 changes: 9 additions & 7 deletions src/wp-includes/html-api/class-wp-html-tag-processor.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1495,14 +1495,22 @@ private function skip_script_data(): bool {

while ( false !== $at && $at < $doc_length ) {
$at += strcspn( $html, '-<', $at );
/*
* Ultimately a SCRIPT closer (`</script>`) must be found or this function will
* return false.
* `</script` is the longest sequence that can be matched, so subsequent length checks
* are redundant.
*/
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@dmsnell dmsnell Aug 5, 2025

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this patch is good, but before we merge, can we also note in this comment that we’re looking for other strings and they are covered here? I think the comment at the moment is slightly misleading, but we also check for <!-- for instance, and it’s currently incidental I think that terminating false is the same for all places within the SCRIPT.

imagine, however, that we wanted to signal something different if we failed to exit the SCRIPT because there was no end-tag vs. that we ended inside some escaped state? then, by returning early at this point we removed our ability to find the <!-- that transitions state.

I believe in review that the code is solid, but I want to make sure we leave this note for the future as a warning to reconsider the check if changing things. I don’t know that these are all currently caught in the tests (which of course would be another great way to cover this risk, by adding new tests for each of these cases, if we can properly think them up).

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@sirreal sirreal Aug 6, 2025

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Good point, I've updated the comment to clarify things.

I do have a number of tests to add to this. I can push them to this branch.

Given how complicated script tag parsing is, I'm tempted to extract them to their own test suite like wpHtmlTagProcessor-scriptParsing. Do you have thoughts on that?

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@sirreal sirreal Aug 7, 2025

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I pulled in your comment changes from #9397 and made some further tweaks. I'm pretty happy with it now.

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@dmsnell dmsnell Aug 7, 2025

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your third example in the comment is perfect. I was probably lazy in not suggesting that in my comment.

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@dmsnell dmsnell Aug 7, 2025

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extract them to their own test suite like wpHtmlTagProcessor-scriptParsing. Do you have thoughts on that?

not that I consider it a huge priority, but I think this is a great idea and would make it clearer for us to be more comprehensive in the tests. I think for every branch of the state machine in the HTML spec we could have data providers generating example inputs for them.

if ( $at + 8 >= $doc_length ) {
return false;
}

/*
* For all script states a "-->" transitions
* back into the normal unescaped script mode,
* even if that's the current state.
*/
if (
$at + 2 < $doc_length &&
'-' === $html[ $at ] &&
'-' === $html[ $at + 1 ] &&
'>' === $html[ $at + 2 ]
Expand All @@ -1512,10 +1520,6 @@ private function skip_script_data(): bool {
continue;
}

if ( $at + 1 >= $doc_length ) {
return false;
}

/*
* Everything of interest past here starts with "<".
* Check this character and advance position regardless.
Expand All @@ -1537,7 +1541,6 @@ private function skip_script_data(): bool {
* parsing after updating the state.
*/
if (
$at + 2 < $doc_length &&
'!' === $html[ $at ] &&
'-' === $html[ $at + 1 ] &&
'-' === $html[ $at + 2 ]
Expand All @@ -1561,7 +1564,6 @@ private function skip_script_data(): bool {
* proceed scanning to the next potential token in the text.
*/
if ( ! (
$at + 6 < $doc_length &&
( 's' === $html[ $at ] || 'S' === $html[ $at ] ) &&
( 'c' === $html[ $at + 1 ] || 'C' === $html[ $at + 1 ] ) &&
( 'r' === $html[ $at + 2 ] || 'R' === $html[ $at + 2 ] ) &&
Expand Down