Login fails with "illegal base64 data at input byte 0" macOS Tahoe

[jotaperez3]

Describe the bug
Login fails with HTTP 500 error and "illegal base64 data at input byte 0" across all browsers. The /api/crypto/public_key endpoint succeeds, but /api/login consistently fails with a base64 decoding error in user/auth.go:90.

To Reproduce

1. Navigate to nginx-ui login page
2. Enter valid credentials
3. Click 'Login'
4. Observe HTTP 500 error

Expected behavior
Successful authentication and redirect to dashboard.

Screenshots
Server logs:

[GIN] 2025/12/25 - 17:56:16 | 200 |     145.062µs |    10.x.x.x | POST     "/api/crypto/public_key"
2025-12-25 17:56:16.414        ERROR        user/auth.go:90        illegal base64 data at input byte 0
[GIN] 2025/12/25 - 17:56:16 | 500 |   88.322415ms |    10.x.x.x | POST     "/api/login"

Browser console error:

AxiosError: Request failed with status code 500
code: "ERR_BAD_RESPONSE"
response: {data: {code: 500, message: "Server Error"}, status: 500}

Request payload structure:

{
  "encrypted_params": "[base64-encoded RSA encrypted credentials]"
}

Info (please complete the following information):

• Server OS: Ubuntu Server
• Server Arch: x86_64 (amd64)
• Nginx UI Version: 2.3.2 1(512) cb1fb69 (go1.25.4 linux/amd64)
• Browser(s): Firefox, Safari, Chrome - all affected
• Browser OS: Tahoe 26.2 MacOS

Additional context
The frontend successfully encrypts credentials and encodes them as base64, but the backend consistently fails to decode the encrypted_params value at user/auth.go:90. This affects all browsers, suggesting the issue is in the backend's base64 decoder rather than browser-specific JavaScript implementations.

[0xJacky]

I am also using macOS 26.2, but this issue did not occur for me. Can you reproduce this problem on other devices?