CORS Policy Error on File Upload After Upgrading to Reflex 0.6.7

[cbiqih]

Describe the bug
Error uploading files via 'rx.upload' : Access to XMLHttpRequest at 'http://localhost:8000/_upload' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

To Reproduce
Steps to reproduce the behavior:

rx.upload(
    rx.flex(
        rx.button("Select file", ),
        rx.text("Drag and drop file here or click button to select file"),
        align='center',
        justify='center',
        spacing='3',
        direction="column",
    ),
    id="import_lexicon_file",
    padding="5em",
    accept={
        "text/csv": [".csv"],
        "text/tab-separated-values": [".tsv"]
    },
    on_drop=SelectFileDialogState.handle_upload(
        rx.upload_files(upload_id="import_lexicon_file")
    ),
    border_radius='1em',
    auto_focus=False,
    max_size=2 * 1024 * 1024, # 2MB
)

Expected behavior
In version 0.6.5, the development can upload files normally, but after the recent upgrade to 0.6.7, this error occurs, I hope to fix it as soon as possible.

Screenshots

Specifics (please complete the following information):

• Python Version: 3.13.0
• Reflex Version: 0.6.7
• OS: macOS 15.2 (24C101)
• Browser (Optional): Chrome 131.0.6778.265 (x86_64)

Additional context
no

[linear]

ENG-4339 CORS Policy Error on File Upload After Upgrading to Reflex 0.6.7

[cbiqih]

The solution given by 'Ask AI' to add cors_allowed_origins was not valid:

import reflex as rx

config = rx.Config(
    app_name="myapp",
    cors_allowed_origins=["http://localhost:3000"],
)