Bug: Double URL Encoding in Presigned URLs for Filenames with Special Characters

When using presigned URLs (presignedUrl: true), filenames containing special characters like brackets, spaces, or other URL-sensitive characters are being double-encoded, resulting in malformed URLs that cannot be accessed.

Bug Details

Affected Version: Current version
Component: getFileLocation() method in index.js
Severity: High - Breaks file access for filenames with special characters when using presigned URLs

Problem Description

The issue occurs in the getFileLocation() method where:

1. Line 242: The filename is encoded using filename.split('/').map(encodeURIComponent).join('/')
2. Line 247: This encoded filename is used to create the S3 key for presigned URL generation
3. Line 255: AWS SDK's getSignedUrl() function internally encodes the key again, causing double encoding

Example

For a filename like doc[123].pdf:

• Expected behavior: Should encode to doc%5B123%5D.pdf in the presigned URL
• Actual behavior: Gets double-encoded to doc%255B123%255D.pdf
  • First encoding: [123] → %5B123%5D
  • Second encoding by AWS SDK: %5B123%5D → %255B123%255D

Root Cause

// Line 242: Pre-encodes the filename
const fileName = filename.split('/').map(encodeURIComponent).join('/');

// Line 247: Uses pre-encoded filename for S3 key
const fileKey = `${this._bucketPrefix}${fileName}`;

// Line 251: AWS SDK encodes the already-encoded key again
const params = { Bucket: this._bucket, Key: fileKey };
presignedUrl = await this.getFileSignedUrl(this._s3Client, command, options);

Impact

• Presigned URLs become inaccessible for files with special characters
• Affects any filename containing: [], (), spaces, and other URL-sensitive characters
• Works fine for regular S3 URLs (non-presigned) because they don't go through AWS SDK's internal encoding

Steps to Reproduce

1. Configure S3 adapter with presignedUrl: true
2. Upload a file with special characters in the name (e.g., "test [file].pdf")
3. Generate a presigned URL using getFileLocation()
4. Attempt to access the URL - it will return 404/AccessDenied

Inspect index.js and start with getFileLocation() around lines 242-255, then trace how the S3 key is passed to presigned URL generation. Reproduce the case with a filename such as doc[123].pdf or test [file].pdf; done means the generated URL contains a single encoding and can access the file.