Rule request: `AvoidSecureStringDisclosure`

As for AvoidUsingConvertToSecureStringWithPlainText it should be avoided to retrieve a PlainText password from a SecureString as it might leave memory trials (or even logging trails).

$Password = $SecureString | ConvertFrom-SecureString -AsPlainText

Besides, the action that follows and requires the plaintext password is likely vulnerable from a security aspect.
This will also include the common used statements as:
(see: https://stackoverflow.com/a/28353003/1701026)

$SecurePassword = ConvertTo-SecureString $PlainPassword -AsPlainText -Force
$BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($SecurePassword)
$Password = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR)
[Runtime.InteropServices.Marshal]::ZeroFreeBSTR($BSTR)

and (see: https://stackoverflow.com/a/40166959/1701026):

$Password = (New-Object PSCredential 0, $SecurePassword).GetNetworkCredential().Password

The general approach of dealing with credentials is to avoid them and instead rely on other means to authenticate, such as certificates or Windows authentication.

Proposed technical implementation details (optional)

Create rules to check for the above mentioned unsafe statements.

首先定位現有的 PSScriptAnalyzer 規則實作和測試，然後比較它們對 ConvertFrom-SecureString、SecureStringToBSTR 和 PSCredential.GetNetworkCredential() 的處理方式。當不安全的 SecureString-to-plaintext 模式能夠被可靠地回報，且相應的分析器測試涵蓋 issue 中的範例時，工作就完成了。