XLSX Invalid Characters Fix

Investigating potential issues

I'm thinking through the error message indicating invalid content in the XLSX file, potentially due to extra or incompatible data. Considering the use of openpyxl for Excel file operations.

Mapping potential issues

I’m working through why opening the Excel XLSX file causes errors, thinking through unescaped or incompatible characters, partial file closure, or repeated workbook usage.

Addressing specific issues

I’m exploring conflicts with default sheet names, Excel's handling of control characters in ASCII data and parsing errors due to malformed hex or ASCII dumps, which could cause the error.

Thought about XLSX generation error for 8 seconds

In almost all cases like this, the culprit is that Excel’s XML-based XLSX files cannot handle certain raw (non-printable) characters. Inside your loop for the “Hex Dump” sheet, you’re feeding potentially invalid XML characters into openpyxl (particularly in the ASCII portion). Those characters might include things like control characters (ASCII 0–31, except for tab/newline/carriage-return) which are not valid in XML and cause Excel to report corrupted content.

Why this happens
When Excel (or any XML-based parser) sees those control characters, it can’t parse the file properly and displays the error:

“We found a problem with some content in XXXX.xlsx…”

Once you click “Yes,” Excel attempts to remove or replace those invalid characters, and the file will open (albeit with those parts sanitized).

How to fix it
You need to sanitize the strings before calling ws_hex.append(...):

1. Strip out non-printable control characters. A quick way is to replace or remove characters outside the valid Unicode range for XML (0x09, 0x0A, 0x0D, plus everything from 0x20 and up).
2. Or at least filter out the known control characters from the ASCII side of the dump.

For example:

import re

def remove_invalid_xml_chars(s):
    # Regex to match valid XML 1.0 characters: 
    # tab (\u0009), newline (\u000A), carriage return (\u000D),
    # plus the “printable” range [\u0020-\uD7FF\uE000-\uFFFD]
    return re.sub(
        r'[^\u0009\u000A\u000D\u0020-\uD7FF\uE000-\uFFFD]+',
        '',
        s
    )

Then in your code:

ascii_part = remove_invalid_xml_chars(ascii_part)
ws_hex.append([offset, hex_part, ascii_part])

This ensures that any raw binary or control characters from your dconf hex dump are removed (or replaced) so that the XLSX can be parsed without errors.

Investigating sources

I’m thinking about why the error might be happening in the XLSX file. It could be due to invalid XML 1.0 characters, newlines, or unsupported formulas.

Assessing potential issues

I'm curious about challenges like inserting too long a string into a single cell, adding characters like '|', or leaving leftover hex dump data.

Identifying character issues

I’m pulling together the idea that control characters in offset or hex_part might be causing the error. Suggesting removing or updating invalid characters from these parts to address the issue.

Addressing sanitization

Key sanitization in "All Keys" and hex dump parts is lacking. Invalid characters in these places could be causing the error.

Ensuring content accuracy

It's worth noting that without sanitizing data like timestamps and event names, invalid XML characters might cause errors. Validating and possibly reformatting might solve these issues.

Ensuring comprehensive sanitation

I’m piecing together that sanitizing all data, including keys, offsets, and hex parts, is crucial to prevent errors from unprintable characters or invalid XML characters.

Thought about invalid XML characters handling for 19 seconds

The most common reason this error persists—despite removing invalid XML characters from the “ASCII” portion—is that other fields may also contain invalid characters (or characters not allowed by Excel’s XML). In your current code, you only call remove_invalid_xml_chars() on some values (e.g., the ASCII portion of the hex dump, the “value” of metadata, etc.), but not on:

• The key fields (e.g., in “All Keys” you only sanitize value, not key).
• The offset and/or hex_part in the “Hex Dump” sheet.
• The logged output strings, timestamps, or any other fields that you’re appending without sanitizing.

If any field in any row contains an invalid XML character, Excel will flag the entire workbook as corrupted.

What to Do

1. Sanitize all strings you write to the workbook—keys, offsets, timestamps, everything. A good rule of thumb is:

   ws.append([
       remove_invalid_xml_chars(str(value)) 
       for value in [field1, field2, field3, ...]
   ])
   

   so that every cell in that row is guaranteed to be clean.

2. Sanitize the “keys” in “All Keys”:

   ws_keys.append([
       remove_invalid_xml_chars(key),
       remove_invalid_xml_chars(value)
   ])
   

3. Sanitize offset and hex_part in the hex dump:

   offset = remove_invalid_xml_chars(offset)
   hex_part = remove_invalid_xml_chars(hex_part)
   ascii_part = remove_invalid_xml_chars(ascii_part)
   ws_hex.append([offset, hex_part, ascii_part])
   

4. Sanitize logged output (timestamps, analyst name, etc.) in “Logged Output”:

   ws_log.append([
       remove_invalid_xml_chars(results["Current Timestamp"]), 
       remove_invalid_xml_chars("Analysis Started")
   ])
   # same pattern for each row you append
   

By ensuring all text you insert is run through remove_invalid_xml_chars(), you eliminate the possibility that hidden control characters or other invalid XML bytes will sneak in and break the workbook.

Why This Happens

The XLSX file format is really a collection of XML files in a ZIP container. If any cell text contains bytes that XML 1.0 disallows (e.g., ASCII control characters 0–31 other than tab/newline/CR), Excel’s parser complains that the file is corrupt. Even a single bad character in a single cell can break the entire file.

Once you sanitize every string, the error about “We found a problem with some content” should disappear.

Investigating corruption

I’m digging into why an Excel file might be flagged as corrupt, considering issues with openpyxl, formulas, formatting, or unexpected data structures.

Identifying corruption causes

I'm curious about potential corruption causes, like using the same variable multiple times, exceeding Excel's sheet title limit, or mixing workbook objects. Checking the file in a text editor or XML inspector might help.

Troubleshooting options

OK, let me see: a massive string, non-printable characters, unexpected objects, regex limits, openpyxl version issues, or workbook locks could be causing the trouble.

Evaluating solutions

I’m considering encoding issues like BOM or data characters, virtual workbook saving, removing unused sheets, upgrading openpyxl, and checking file names or paths to resolve the corruption.

Pinpointing potential solutions

I'm weighing explicit cell encoding, older openpyxl versions, missing or None keys in 'results,' checking Excel logs for clues, and examining invalid styles or formatting.

Testing new options

Creating a new workbook or examining XML in 7zip can pinpoint issues. Also, trying XlsxWriter might yield better results.

Trying another way

I’m testing openpyxl updates, addressing large strings, using escape functions, incrementally building workbooks, and considering removing line breaks to resolve corruption issues.

Thought about sanitizing all fields for 15 seconds

Potential Reasons & Debugging Steps

Even with all strings being sanitized, Excel can still report corruption in certain scenarios. Here are some additional (and somewhat hidden) causes you should check:

1. There might still be invalid characters slipping through

• Ensure you are importing re only once at the top of the file and not inside the function, or at least consistently.
• Double-check your remove_invalid_xml_chars() function covers all invalid Unicode ranges for XML 1.0. (For instance, if you are dealing with surrogate pairs or characters outside the Basic Multilingual Plane, it can be trickier; \uD800-\uDFFF are surrogate code points that can also cause trouble in XML.)

Tip: You can insert a quick debug print in your loop to spot-check the sanitized values:

cleaned_value = remove_invalid_xml_chars(original_value)
if cleaned_value != original_value:
    print(f"Sanitized something:\nOriginal: {repr(original_value)}\nCleaned: {repr(cleaned_value)}")
ws.append([cleaned_value])

If you see something suspicious, that might still be your culprit.

2. A non-string object is sneaking in

Sometimes if a value is not a string (e.g., None, a dictionary, or a list), openpyxl might mis-handle it or attempt to coerce it into a string in ways that produce invalid XML. Make sure everything you write to the cell is a proper string, especially if you are iterating over something like for key, value in metadata.items():.

Quick check:

for key, value in metadata.items():
    if not isinstance(key, str):
        key = str(key)
    if not isinstance(value, str):
        value = str(value)
    ws.append([remove_invalid_xml_chars(key), remove_invalid_xml_chars(value)])

3. Worksheet names

• You are already sanitizing them, but keep in mind that Excel limits sheet names to 31 characters. Also, certain characters ([ ] : * ? / \) are disallowed in sheet names. If you have a result dictionary key that attempts to create a sheet name longer than 31 characters or with invalid symbols, Excel can flag it as corrupt.

4. Extremely long cell values

In very rare cases, extremely large cell values (multiple megabytes of text) can trip up Excel. If any single “ASCII dump” line is huge, consider splitting it or just confirm it’s not unreasonably large.

5. A style or formula corruption

If you (or openpyxl by default) are applying styles or formulas with invalid references, it can lead to “We found a problem with some content.” This is less common with the usage above, but worth checking if you have extra code that’s not shown.

6. The file is truly being corrupted upon save (I/O issues)

Verify that:

1. You’re not re-opening or overwriting a file while it’s still in use.
2. You’re not saving multiple times to the same path in quick succession.
3. You have the correct permissions (especially on Windows).
4. The version of openpyxl is recent. Older versions have had known issues.

7. Find exactly where corruption occurs (Incremental Debugging)

If all else fails, do incremental (step-by-step) workbook building:

1. Create the workbook and save just the “Analysis Results” sheet. Open in Excel. Does it work?
2. If yes, add the “File Metadata” sheet. Save. Open in Excel.
3. Continue adding one sheet at a time until you hit the corruption. The last sheet (or row) you added is the culprit.

Often, you’ll discover that one row (e.g., a single line in your hex/ASCII dump) is injecting something invalid that your regex hasn’t stripped. Or maybe a key has an unusual character. This step-by-step approach is the most reliable way to isolate the root cause.

Summary

1. Sanitize everything—including keys, offsets, timestamps, sheet names, etc.
2. Check for non-string objects (convert them to strings first).
3. Watch out for invalid sheet names or extremely large text.
4. Incrementally debug by building your workbook one sheet at a time until you spot the problem.

One of these steps will almost certainly pinpoint where the corruption is sneaking in, and from there, you can handle or sanitize it properly.