Hello Daniel,
So as I've mentioned we got a response parameter from an API, and we already have decode the parameter value using this extension:

It works, but we're using this parameter value to be rendered as HTML tag, and in order to render an image inside HTML tag the URL cannot consists of Ampersand character, it needs to be replaced as %26. Therefore, I want to try using Regex because I think the replacement condition quite difficult since the URL text is inside an attribute/parameter.
I can give you an example of the parameter format after decodeURL action:
"detail": "<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. & Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.<img src="/content/dam/p&t/2019/juli/Telkomsel%20Gelar%20Hackathon%20Innovate%202019_2.JPG" style="font-size: 0.8125rem;"> Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore & et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
<img src="/content/dam/p&t/2019/juli/Telkomsel%20Gelar%20Hackathon%20Innovate%202019_4.JPG" style="font-size: 0.8125rem;>" </p>"
I'm also give you the sample as an image in case the Ampersands characters are converted automatically in OS forums editor:

Thank you