CAPTCHAs, displays that match the "if" clause of the third bullet, can claim conformance under the first bullet by simply saying in the ALT text "image to test if you are a human." It is not just nor do I believe it is the authors' intent to open up this loophole.
Close loophole by repairing the first bullet along the lines of the previous comment.
Thank you for your comment. We have modified 1.1.1 as follows:
1.1.1 Non-text Content: Except for the situations listed below, a text alternative that presents equivalent information is provided for all non-text content.
* Controls-Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (See also Guideline 4.1 Support compatibility with current and future user agents, including assistive technologies)
* Media-Test-Sensory: If non-text content is multimedia , live audio-only or live video-only content, a test or exercise that must be presented in non-text format , or primarily intended to create a specific sensory experience , then text alternatives at least identify the non-text content with a descriptive text label. (For multimedia, see also Guideline 1.2 Provide synchronized alternatives for multimedia.)
CAPTCHA: If the purpose of non-text content is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided and alternative forms in different modalities are provided to accommodate different disabilities.
* Decoration-Formatting-Invisible: If non-text content is pure decoration, or used only for visual formatting, or if it is not presented to users, then it is implemented such that it can be ignored by assistive technology.