Downloaded excel exports have an extra byte before the "PK" marker of xlsx

[smil2k]

What happens?

In case I would like to export the results to excel, then the excel cannot be opened due to an extra byte in front

To Reproduce

load excel;
copy (SELECT extension_name, installed, description FROM duckdb_extensions() ) to 'export.xlsx' (format xlsx);
.files download export.xlsx

Attached the corrupt export.xlsx
Removing the extra byte fixes the problem.

Browser/Environment:

Version 141.0.7390.123 (Official Build) (arm64)

Device:

MacBook Pro M3

DuckDB-Wasm Version:

@duckdb/duckdb-wasm@1.31.1-dev1.0

DuckDB-Wasm Deployment:

shell.duckdb.org

Full Name:

Tamas Cserveny

Affiliation:

User Story Kft

[humphd]

Came here to report the same problem. I've temporarily fixed it in my code by stripping the first byte:

buffer = await duckdb.copyFileToBuffer(tempFilename);
if (buffer[0] !== 0x50) {
  console.warn("Removing leading byte from XLSX buffer");
  buffer = buffer.slice(1);
}