generate_presigned_post presigned url upload is failing with invalid policy condition if key contains $$

[asvashrith]

Describe the bug

We have file naming convention of keeping 2 "$$" as prefix or suffix such files are failing with Invalid policy condition of key when we upload them using presigned url generated from gemerate_presigned_post

s3_client = boto3.client('s3',api_version='2006-03-01',config=boto3.session.Config(signature_version='v4'))
response = s3_client.generate_presigned_post(
        Bucket="sample_bucket",
        Key="Folder/filename$$.txt",
        Conditions=conditions,
        Fields=fields,
        ExpiresIn=url_exp_time,
    )

AccessDeniedInvalid according to Policy: Policy Condition failed: ["eq", "$key", "/2025/0267$$Copy.csv"]

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

File should be uploaded even if it has $$ in the name or any other special characters as well.

Current Behavior

if key contains 2 dollar symbols consecutively then upload is failing here is a sample key "Business/new/abcd$$.pdf"

Reproduction Steps

Generate presigned post url pass Key with consecutive $$ for example: "new/abcd$$.pdf"

With presgined url trying uploading we'll get Invalid policy condition exception

Possible Solution

No response

Additional Information/Context

No response

SDK version used

1.37.38

Environment details (OS name and version, etc.)

Python and 3.11

[RyanFitzSimmonsAK]

Hi @asvashrith, thanks for reaching out. I was able to reproduce the behavior you've observed. I've reached out to the S3 service team about this potential bug, and will let you know when I receive any updates.

Ticket # for internal use : P230041718