HTMLStripCharFilter (since 10.5.0) treats a start tag whose name only begins with script, style or br (<scripts>, <style-guide>, <stylesheet>, <brand>) as a script, style or br tag, so it silently drops all text after it up to the next </script> or </style> (often to the end of the value) and misapplies escapedTags to such names

Finding LFV-780Area: analysis / HTMLStripCharFilter (JFlex grammar: the BR, SCRIPT and STYLE start-tag rules of the LEFT_ANGLE_BRACKET state; also the 'htmlStrip' char filter SPI)Priority: mediumImpact: silent wrong resultsNovelty: new

Finding page for LFV-780

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You strip '<scripts>hello</scripts> world' (or '<style-guide>hello</style-guide> world') with HTMLStripCharFilter and expect '\nhello\n world', which is what Lucene 10.4.0 gives and what main gives for the same shape with any other name, such as '<scrapes>'. Since 10.5.0 the output is empty: the start-tag rules for script and style no longer require a delimiter after the name, so the longer name is taken for a <script> or <style> tag and everything up to the next literal </script> or </style>, here the end of the input, is dropped (for '<stylesheet>hello</stylesheet> world' a StandardTokenizer after the filter emits no token at all). With escapedTags={brand}, '<brand>Acme</brand>' likewise comes out as '\nAcme</brand>' instead of unchanged.

The test shows that HTMLStripCharFilter (since 10.5.0, #15756) takes a start tag whose name only begins with script (<scripts>) for a <script> tag and drops everything after it up to a </script> that never comes.

Expected vs actual

Expected "<scripts>hello</scripts> world" to strip to "\nhello\n world" (what 10.4.0 gives, and what main gives for any other name); actual "" (expected:<[\nhello\n world]> but was:<[]>), with -ea and -da.

Files

• src/org/apache/lucene/analysis/charfilter/TestHTMLStripScriptPrefixName.java (JUnit test)

Run it

• Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
• Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
• Recorded outcome of run 1 on Lucene main 645d4fe14a20: 1 test(s) run, 1 failed.
• How to read the outcome: a failing test is the finding reproducing (the failure message states expected against actual).
• Seeds: a rerun with the same seed replays the same random choices. Assertions off (-da -dsa -Dtests.asserts=false) is the production-like setting.

# Lucene checkout at the tested commit, built with: ./gradlew --no-daemon assemble   (JDK 25)
LUCENE=/path/to/lucene; V=12.0.0-SNAPSHOT
CP=$LUCENE/lucene/core/build/libs/lucene-core-$V.jar
CP=$CP:$LUCENE/lucene/codecs/build/libs/lucene-codecs-$V.jar
CP=$CP:$LUCENE/lucene/test-framework/build/libs/lucene-test-framework-$V.jar
CP=$CP:$LUCENE/lucene/analysis/common/build/libs/lucene-analysis-common-$V.jar
CP=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar   # test-framework dependencies (Maven Central)
CP=$CP:junit-platform-console-standalone-6.1.3.jar   # JUnit Platform console launcher (Maven Central)

javac -d classes -cp "$CP" $(find src -name '*.java')

# run 1: assertions on, seed DEADBEEF
java -ea -esa --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=DEADBEEF \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.analysis.charfilter.TestHTMLStripScriptPrefixName

Gradle alternative: copy the test into the matching module's src/test/ tree of the checkout and run ./gradlew -p lucene/<module> test --tests <class> -Ptests.seed=<seed> (add -Ptests.asserts=false for a run without assertions).

Feedback

Open an issue in lucene-ai-bug-hunt. Please do not open issues or pull requests in apache/lucene about this finding unless a Lucene committer agrees it should be filed.

Snapshot of 2026-11-03. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.