vishalcoc44 opened a new pull request, #1025:
URL: https://github.com/apache/poi/pull/1025

   ### Summary
   This PR adds a context-aware fuzz target for the Apache POI 
`WorkbookEvaluator` engine to the `poi-fuzz` module.
   
   This fuzzer was developed as part of Google's OSS-Fuzz integration (see 
google/oss-fuzz#14987) and is being upstreamed 
   
   ### Technical Approach
   - **Context-Aware Strategy**: Pre-populates a **20×20 Excel data grid** with 
a diverse mix of numbers, negative values, strings, booleans, and error codes 
so that referential formulas (SUM, VLOOKUP, INDEX, MATCH, etc.) exercise real 
evaluation paths instead of fast-failing on empty references.
   - **Guided Input Generation**: Uses a dictionary of **60 complex Excel 
function signatures** to steer the fuzzer toward deep calculation branches in 
the `WorkbookEvaluator`.
   - **Coverage Impact**: In local testing, this increased code coverage within 
the `WorkbookEvaluator` from **19 lines** to over **2,200 lines** (~11,700% 
increase).
   - **Security Alignment**: Expected exceptions (`FormulaParseException`, 
`NotImplementedException`, etc.) are suppressed while internal logic flaws 
(NPE, OOB) bubble up as findings.
   
   ### Placement
   File added to 
`poi-fuzz/src/main/java/org/apache/poi/fuzz/WorkbookEvaluatorFuzzer.java`
   ### Related
   - OSS-Fuzz integration PR: https://github.com/google/oss-fuzz/pull/14987
   


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